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(Geological Seuies, L) 




Reprinted with the permission of the original piibHsher 


New York 

i-njT-IK^i ■ 



Printed in U,S.A 



No. 1. — Notey on the Geology of the Iron and Copper Distriets of Lake Supe- 
rior. By M. E. Wadswoktu. (0 Tlutes) 

No, 2. — The Eelsiles and their Associated Koclcs, North of Boston. By J. S. 




No. 3. — On an Occurrence of Gold in Maine. By M. E. WAiJSw'oiiTit . . 181 

No. 4. — A Microscopical Study of the Iron Ore, or Poridolite of Iron-Mine 
Hill, Cumberland, Rhode Islaud. By M. E. Wadswouth .... 183 

No. 5. — Observations upon the Physical Gcogniphy and Geology of Mount 
Ktaadn. By C. E. Hamlin. (2 Plates) 

. 189 

No. G. 

-Keport on the Peccnt Additions of Eossil Plants to the Museum Col- 
lections. By LliO EEHQUlilUEUX .... 

. 225 

No. 7. — The Great Dike at Hough's Neck, Qniucy, Mass. By John Eliot 



No. 8. — On some Specimens of Permian Eossil Plants from Colorado. By 
Leo Llsquerkux ..... 

. 243 

No. 0. — On the Relations of the Triassic Traps and Sandstones of the Eastern 
United States. By William Mouuia Davis. (3 Plates) 

. 249 

No. 10. 

-'I he Folded ITcIderberg Limestones, East of the Catskills. By 
William Moiims Davis. (2 males) 

. Sll 

No. lI. — ThG Azoic System and its Proposed Subdivisions. By J. D. 
Whitney and M. E. Wadswoutu 


Bulletin of tke Museum of Comparative Zoology, 


Whole Skrtks, Vol. VII. 

(Geological Series, Vol. I.) 

No. I. 








July, 1880. 

r ■ 






Historical 1-26 

HisTOiucAL Summary 20, 27 

Metiioi>s of Orservation . 

^1 28 

The Jasi'kr a^^v^ Iron Ore 28-36 

The Basic Intrusive Rocks, Schists, and Felsite 


" Soft Hematites " 49-52 

Granite, Gneiss, and Quart/ite 

Potsdam Sandstone 


Fkrido'iitk and Serpentine GO-66 

General Discussion and Results 



Historical 76-107 

Historical Summary 107-109 

The Traps 109-113 

The Sandstones and Congloinierates 
The Veins and Copper Deposits . . 








No. 1. — Notes on the Geology of the Iron and Co2)peT Districts of 

Lake Superior, Ey M. E. Wadswoktil 

There are probably no regions of like extent in the United States that 
Lave attracted greater interest or attention than the Copper and Iron 
districts of Lake Superior. The most discordant views have been held 
concerning their geology, and the origin of their ore deposits. There 
are also probably no districts in this conntry which have been more accu- 
rately studied, taking all of the conditions into consideration, than these 
were some thirty years ago. The geology, including the origin of their 
ore deposits, was then, for the time and methods of study, stated with a 
remarkable degree of accuracy, so far as it has been our province to 
observe or judge. It would not, then, be our duty to write concernino- 
these districts, were it not that the almost universal belief of geolo<nsts 
at the present time regarding one, and in some respects the other dis- 
trict, is so entirely at variance with the facts as we interpret them. 
Before giving the facts it is necessary to present to the reader some of 
the various ideas held regarding the geology of both districts. We shall, 
however, in the main confine ourselves to those parts which we have 
visited, except so far as observations elsewhere have a bearing upon our 
work, or upon the questions which we wish to discuss. 

It seems best to take up these views In chronological order, even if it 
does impart a dictionary flavor to this paper. First in order, then, wo 
propose to discuss 

The Iron District. 

The earliest writer that it is necessary to quote here is TTcnry E. 
Schoolcraft, wliose Narrative Journal of Travels, etc. was published at 
Albany in 1821. He speaks of tlie granite at Granite Point (p. 158), 
and of its being traversed by veins of greenstone trap. He gives the 
composition of the former rock, and advances his reasons for considerinf^* 
that it occupied its present position before the deposition of the over- 
lying sandstone. He does not attempt to give the age of the sandstone, 

althougli he tliinks "its position would indicate u near alliance to the 
' old red sandstone.' " 

VOL. VII. — KO. 1. 





Dr. Douglas Hongliton, in his first Report on the Geology of Miclii- 
gau, remarks upon the "appearance of primary and, trap rocks forming 
mountain cliaius, and tlio groat disturbance which has taken place 
since the deposition of the red sandstone," and says tliat this sandstone 
in the vicinity of Granite Point is "scarcely disturbed, resting upon 
nobs of primary rocks." * In Dr. Iloughton's Fourth Annual Report, 
for 18.11,t tlie rocks of this region are described as primary ones, con- 
sisting chiefly of granite, sienite, sienitic granites, and greenstone witli 
metamorphic rocks on their flanks, forming a stratified series consist- 
ing of "talcose, mica and clay slates, slaty hornblende rock, and quartz 
rock ; the latter rock constituting by far the largest proportion of 
the whole group." He considered tliat the granite passed "ahiiost in- 
sensibly into a serpentine rock." {I. c, p. 482.) In like manner, he 
thought that the granites on the soutlicastcrly side of the district 
changed going northwesterly into a greenstone, and tluit the dikes trav- 
ersing these granites were identical with the greenstone, having been 
injected into the granite. His serpentine bears a close resemblance to 
greenstone, and he states that " possibly a more close examination may 
show it to be a simple series of dUics, lying parallel to the hnc of cleav- 
age of the slate rocks." {I. c, p. 494.) Regarding Tresque Isle he says : 
""rhis point of land has its origin from the simple elevation of a mass of 
trap rock, which rises on the north in abrupt cliffs, varying from twenty 
to sixty feet in height. The trap is mostly greenstone, though portions 
of it are so largely impregnated with a dark-coloi-cd, almost black ser- 
pentine, as to deserve the name of serpentine rock. The knob of trap 
under consideration is possessed of additional interest, from the un- 
equivocal evidence of uplift, as also from the manner in which these 
evidences are exhibited. The cliffs of trap occupy the very extremity 
of the point, while the neck and central portions are made up of con- 
glomerate or trap tuff and sand-rock, resting .nptm the trap. These 
upricr rocks also appear upon the immediate coast, in cliffs of from 
twenty to sixty feet in height, and in many places they are seen resting 
directly upon tlic trap. The stratification of those sedimentary rocks 
has been very much disturlied, and they invarialily dip, at a high angle, 
in all directions from the trap itself. The character of liotli rocks, at the 
immediate line of junction, is almost completely lost, and the evidences 
of change most unequivocally marked. But the most curious feature 
of the whole is, that the sedimentary rocks, for a distance of several 

« History of Micliig™, T.y ,T. H. Lunmaii, (New York, 1S39,) pp. 318, 352. 
t Joint Docuun-nls, Jliefiig;iii, 1811, pp. 471-007. 





hundred feet, have been completely shattered or broken into minnte 
fragments, which, having retained their original position, were again 
cemented by the injection of calcareous matter. This injection lius 
filled the most minute fissures, and so perfect is it, that, in looking upon 
the face of a mural clill of these rocks, the veins may be easily seen at 
a distance of many rods, forming, as it were, a complete net-work over 
the clitf, and so minute is it, that a single hand specimen frequently 
contains many hundreds of these veins." (L c, p. 492.) 

In this Report is the first mention of iron ore in this district that we 
have seen. He gives amongst the minerals of tlie " Metamorphic group 
of Kocks/' "scaly red oxide of iron" and "hajmatite." Ecgarding the 
latter ho says: "Although the haematite is abundantly disseminated 
through all tlie rocks of metamorphic group, it does not appear in 
sufficient quantity, at any one point that has been examined, to be of 
practical importance." (/. c, p. 504.) 

In Dr. Houghton's Fifth Report some remarks were made both 
upon this district and upon the copper district, but nothing of special 
importance was added.* Mr. George N. Sanders, in a report to the 
Ordnance Office,t speaks of collecting "rich specimens of irgn ore" on 
the Menomonee River. In the same documents for 1845 - 46 % are given 
reports for the year 1845, by William A. Burt and Bela ITubbard.§ Mr. 
Hubbard evidently considered that the ridges in the Marquette Iron 
District were composed in the centre of eruptive rocks, but not outcrop- 
ping, being "capped as well as flanked by the metamorphosed rocks." 
He states in regard to the metamorphic rocks that "these rocks are 
throughout pervaded by the argillaceous red and micaceous oxydes of 
iron, sometimes intimately disseminated, ana sometimes in beds or 
veins. These are frequently of so great extent as almost to entitle them 
to be considered as rods. The largest extent of iron ore noticed is in 
township 47 north, range 26 west, near the corners of sections 29, 30, 31, 
32. There are here, too, large beds or hills of ore, made up almost entirely 
of granulated, magnetic, and specular iron, with small quantities of spa- 
those and micaceous iron. The more northerly of these hills extends in 
a direction nearly east and west, for at least one fourtli of a mile, and 

* Joint Documents, Michi^cjan, 1842, pp. 436-441. 

t Senate Docnineiita, 28tii Cong. 2(1 Scss., 1844-45, XL, Poc. 175, p. 11. 

X 29tli Cong. 1st Scss., VH., Doc. 357. 

§ See also Senate Documents, 184!)~50, 31st Cong. 1st Sess., TIL 802-842, and 
The Mineral Region of Lake Superior, hy J. Houghton and T. M^ Bristol, (Detroit, 
184G,) pp. 3-39, 



has a breadth httic less than 1,000 feet, the whole of which forms 
a single mass of ore, with occasional thin strata of imperfect chert 
and jasper, and dips north 10 degrees, cast about 30 degrees. At its 
southerly outcrop, the ore is exposed in a low cliif, above which the 
hill rises to the height of 20 or 30 feet above the country on the 
south. The ore here exhibits a stratified or laminated structure, and 
breaks readily into sub-rhomboidal fragments, in such a manner as will 
greatly facilitate the operation of quarrying or mining the ore. 'iliis 
bed of iron will compare favorably, both for extent and quality, with 
any known in our country." (p. 22.) The sandstone is said to be found 
frequently ''surrounding, and in contact with, the uplifted masses of 
igneous rocks, and is then invariably much altered both in appearance 
and textures, and may, under such circumstances, fairly be considered aa 

metamorphic." (p. 23.) 

In the report of Mr. A. B. Gray to the Ordnance Bureau,* galena and 
copper pyrites were said to exist quite abundantly, and that it was prob- 
able that rich tin ores would be found, Mr. Samuel Peck is credited with 
having first explored the iron region, and called attention to the exist- 
ence of that mineral {I. c, pp. 15, 16). 

Prof. H. D. Bogerst stated that the rocks in the vicinity of the 
Chocolate and Carp Bivers (Huronian of Brooks) were 'Hhe equivalents 
undoubtedly of the Primal sandstone and Primal slate," or the Potsdam 
sandstone of the New York survey. 

Mr. William A. Burt, in his report "with reference to mines and 
minerals for 181G,"t (pp. 849-852,) described "fourteen beds of mag- 
netic iron ore" in this district. Mr. Bela Hubbard in his report for the 
same year {l. c, pp. 001 - 905) advances some views upon the passage of 
one rock into another, as follows : "A feature peculiar to all the rocks of 
the country alluded to as granitic, is their occasional trappose character, 
and the rare occurrence of mica. The constituents which make up the 
greater part are quartz, felspar, and hornblende; the proportions of 
which vary extremely. Thus, while the general character is that of true 
sienite, the absence of quartz in a distinct form often produces a green- 
sione, while frequently the last-mentioned mineral predominates almost 
exclusively, constituting a true hornblende rock, which is generally of 
a crystalline structure, and usually has a slaty cleavage. Again, quartz 

* Executive Documents, 20th Cong. 1st Scss., Vol. VIL, No. 211, 1845-46, pp. 
2-23. Am. Jour. Sci., (2,) Vok V., 1848, p. 151. 
t Proc. Bost. Soc. Nat. Hist., April 1st, 1846, II. 125. 
t Senate Documents, 31st Cong. 1st Seas., 1849-50, III. 371 - 935. 





becomes the predominant mineral, constituting what may be denomi- 
nated a quartzite In a few instances talc was found to take the 

place of hornblende, constituting a j)n)to<jim We accordingly find 

the sienitcs assuming a trappose character, and often undergoing so in- 
sensibly the change from a granitic to trappean rock, that it is impossible 
to distinguish where one begins, and the other ends. In the operation 
of these changes, the excess of silica may bo called in to account for 
the metamorphic rocks of the country, and particularly for the abun- 
dance of pure quartz in rocks and veins Not only have 

changes accompanied the contact of trap with other rocks, such as 
have usually been referred to the heat of the injected mass when 
in a state of fusion, but equally marked changes have accompanied 
the conjunction of the ue.}dtes with the sandrock under circumstances 
where the same causes cannot be called in; for the latter gives evidence 
of having been deposited subsequently to the formation and uplift of 
the former, and the sienite was as often observed to have partaken of the 
cliango as the sedimentary rock. Without going further into detail of 
facts of merely scientific nature, it may be sufficient to say that it seems 
more reasonable to attribute the mctamorphism which has taken place 
m both rocks rather to galvanic and chemical action than to igneous 
causes, whicl^ are so generally called in to account for all these phenom- 
ena. The rocks designated upon the maps as metamorphic, occupy, 
as it were, beds amid the surrounding primary rocks ; and while we 
would avoid any theoretic conclusions as to their origin, it may be stated 
that, throughout the whole primary region, the limits of each rock, 
except in the case of dikes, are seldom distinctly defined, but one passes 
mto the other by gradual transition; so that often rocks of distinct 
name and character can be considered only as members of the same for- 
mation, the constituents of which have become differently aggregated." 
Mr. J. W. Foster, in his report to Dr. Charles T. Jackson, dlted Sep- 
tember 28, 1848,* describes part of the iron region. The rocks are con- 
sidered to be older tiian the sandstone, which is regarded as belonging to 
the oldest paleozoic rocks. Previous to this. Dr. John Locke attemp'tcd 
to describe the district in part ; but his account appears to be of no 
value, except from an historical point of vicw.f We would, however, call 

attention to his bathetic description of the " Pictured Eocks " Cpn 189 ^ 
191). ^^^* 

* Senate Docunionts, 2(1 Scss. SOih Cong., 1848-49, III., Doc. 2, p]). 159-1G3 ; 
Executive Documents, III., Doc. 12, pp. 159-163. 

t Senate Documents, Ist Sess. 30tk Cong., 1847-48, II. 180-189, Oct. 25, 1847. 



Pages 371 - 801 of a publication previously mentioned* is devoted to 
the publication of the reports of Dr. C. T. Jackson and his corps. This 
document is one of the curiosities of geological literature, — a vara avis. 
It was printed in such a manner that in many cases it would be very 
difficult, if not impossible, to determine who were the autliors of the 
difierent parts of the text, were it not for the fusiUade all along the line. 
Dr. Jackson gives (pp. 477 - 479) some account of his first knowledge 
of tlie iron ore (1844) in this district, but it seems that he never visited 
the region himself Dr. John Locke, iu his field-notes for 1847 (l. e., pp. 
572- G05), describes the rock of Prcsque Isle as " a light-green trap, re- 
ticulated with white veins near the junction of the sandstone, with which 
the trap is apparently interfused." He also describes the iron region to 
some extent. He considers that the trap rocks are frequently interfused 
with the metamorphic cues in the district, and states that certain quartz 
veins "deserve close examination for gold, silver, and other rare metals. 
Veins of this description, if they prove important, can undoubtedly be 
found in the metamorphic rocks." 

It is well known that the early explorers had tc contend with very 
great difficulties in their work in this region ; but probably none ever 
suffered such aggravation of spirit as did Dr. Locke, when, on July 27, 
1847 his compass ran wild and its poles stood seventeen feet and eight 
inches apart, unless it was when he found his provisions were only a few 
sticks of wood and a bucket of bean soup.t Mr. J. W. Foster, m his 
report to Dr. Jackson, dated May 26, 1849 (1. c, pp. 773 - 78.5), gives 
a description of the iron region, as studied by him in 1848. He regards 
the iron ores as sedimentary deposits. " These bods, so for as I have 
observed, present a marked similarity in mineralogical characters, and 
derive their origin from common causes, and those were aqueons. The 
jointed structure and waved stratification of some of the beds prove that 
ir^neous causes have operated, since their deposite, to modify and change 
their character." (p. 776.) « Here, they certainly bear upon their sur- 
faces strong marks of thcii mechanical origin. They are regularly 
stratified, and often contain thin scams of silcx in mmuto grams, so 
that a specimen, on its cross fracture, resembles ribbon-jasper. The 
lines of stratification can readily be distinguished from those of lamma- 
tion. Like the slates, they are often found contorted and wrinkled, and 
the same facts could be adduced in both cases to prove their common 


(p. 770.) This description belongs, for the most part, to the 

* Senate Documents, lat Soss. 31st Cong., 1849-50, ITI. 371-935. 

t Senate Documents, 1st Sess. 30th Cong., 1847-48, IT., Doc. 2, p. 190. 

r-'' P 



McnomoncG region, but part of the Marquette district is included. The 
.granites wcrechissed by him as igneous rocks. 

Printed in the midst of these reports is one from lAIcssrs. Foster and 
Whitney (/. c, pp. G05-G2G) made to the Land Office and Interior De- 
partment, dated November 5, ISiO, which gives some account of the Iron 
and Copper districts. The iron is slated to occur in tiie mctamorphic 
formation. "This formation consists of hornblende, talcose, and chlorite 
slates, with associated beds of hornblende and felspar rocks, evidently 
trappeau in their origin." (pp. GOD, GIO.) 

December ID, 184D, Professor J. D. Whitney gave some account of 
this region before the Boston Society of Natural History.* Tlio iron 
ore was then stated to be of igneous origin. In a ''report traus^ 
mifctcd to the Interior Department, October 25, 1850,t Messrs. Fos- 
ter and Whitney state that the sandstone is of Potsdam age. '^Eolow 
the whole of the silurian rocks we meet with a class 'of deposites 
which were probably detrital in their origin, but which have been 
so metamorphosed as essentially to change their structure. They are 
destitute of organic remains, and contain imperfect traces of strati- 
fication. They consist of various schists and beds of quartz, marble, 
and specular and magnetic oxide of iron. We have termed tlicsc vari- 
ous groups the azoic system, ^n. system which, thus far, has not been 
fully recognized in Europe, but the existence of which tlie results of this 
survey, as well as that of Canada under Mr. Logan, have fully demon- 
strated. Upon the upturned edges of those slates the Potsdam sand- 
stone is found reposing in a nearly horizontal position. TJu^y form 
the nucleus around which the newer rocks have boon deposited, and 
arc extensively developed between the shores of the two lakes. They 
are the depositories of the most extensive beds of iron known in the 
world."i 'i'lio term '' Laurontian " was first proposed by Sir William 
E. Logan, in 1853,§ for the mctamorphic rocks underlying the Pots- 
dam sandstone north of the St. Lawrence, although it had^'been used 
some years before by Mr. Edward Dcsor to designate certain drift de- 
posits in the St. Lawrence valley, and by the law of priority the name 
should have been retained in its original sense. 

May 5, 1851, a paper was presented to the American Association || 

* rrococdings, TIL 210-212. 

t Senate Docmuoiits, 2(1 Scss. 31st Cong., 1350-51, IT., Doc. 2, pp. 147-152. 
X See also Bulk Soc. GcoL Franco, 1850-51, (2,) VIII. 89-100. 
§ llcport of Prof^n'eys Geol. Survey of Canada, 1852-53, p. 3. 
Trocccdings, V. 4-7. 



by Messrs. Foster and Whitney, entitled, "On the Azoic System, 
as developed in the Lake Superior Land District," in which the dis- 
tribution of the azoic rocks in North America was briefly pointed 
out. The term Azoic was adopted liy them from Murchinon and De 
Verneuil,* but limited in its signification by Foster and Whitney 
"to a class of rocks supposed to be dctrital in their origin, and to 
Lave been formed before the dawn of animal or vegetable life. It 
comprises the most ancient of the strata which form the crust of the 
earth, and occupies a distinct position in the geological column; being 
below the Potsdam sandstone. In this district, the rocks consist, for 
the most part, of gneiss, hornblende, chlorite, talcose, and argillaceous 
slates ; interstratified with beds of quartz, saccharoidal marble, and im- 
mense deposits of specular and magnetic oxide of iron. Most of these 
rocks appear to be of dctrital origin, but to have been greatly transformed 
by long-continued exposure to heat. They arc sub-crystalline, or com- 
pact, in their texture, and rarely present unequivocal signs of stratifica- 
tion. They have been subject to the most violent dislocations. In one 
place, the beds arc vertical ; in another, reversed; and in another, present 
a scries of folded axes. Intermingled with them is a class of rocks 
whose igneous origin can hardly be doubted, and to whose presence the 
metamorphism so characteristic of this series is, in a measure, to be 
ascribed. They consist of various proportions of hornblende and feld- 
spar, forming traps and basalts; or, where magnesia abounds, pass into 
serpentine rocks. They appear, in some instances, to have been pro- 
truded through tlie pre-existing strata, in the form of dikes or elvans; 
in others, to have flowed in broad lava streams over the ancient surface; 
and in others, to have risen up through some wide-expanding fissure, 
forming axes of elevation." Gaseous sublimations, intense pressure, and 
eicctro-chernical agencies were thought to have assisted in the metamor- 
phism, as well as the plutonic masses. *' Since the theory of metamor- 
phism has been generally adopted, many of tlie rocks whicli were for- 
merly regarded as igneous are now referred to aqueous agency, and 
their transformations traced to the presence of erupted rocks. They 
here cited numerous examples of metamorphism, showing that argdla- 
ccous schist is transformed into gneiss; sandstone into compact vitreous 
quartz; and limestone into saccharoidal marble, when brought in con- 
tact with eruptive masses. Tliey therefore inferred, that those obscurely 
bedded rocks, — such as gneiss, and the crystalline schists, —were of 
sedimentary origin ; that no rock was to be regarded as igneous, unless it 

* Russia and the Ural Mouniains, I. 10. 



occur In vust, irregular masses, like granite ; in dome-shaped, or crater- 
like summits, as basalt, or trachyte; in long lines, as dykes or elvans 
catting through the incumbent strata; in ramifying veins, like granite; 
or broad lava sheets, like trap. Many eminent geologists maintain that 
the lowest stratified rocks are but portions of the Silurian System, and 
that, from long^continued exposure to heat, the lines of stratification 
have become obscure, and all traces of organic remains obliterated. Our 
observations in this district (they remarked) have led us to a diirorcut 

"The evidence is ample that the base of the Silurian System reposes 
upon their upturned edges, and that the causes by which the metamor- 
phism of the former was eflected had ceased to operate before the depo- 
sition of the latter. Between the two systems there is a clear and well- 
defined line of demarkation. It forms one of those great epochs in the 
history of the earth, where the geologist can pause, and satisfy himself 
of the correctness of his conclusions. On the one hand he sees evidence 
of intense and long-continued igneous agency, and, on the other, of com- 
parative tranquillity and repose The Azoic Series was characterized 

by immense deposits of specular and magnetic oxide of iron. This might, 

with great propriety, be denominated the Iuon Age of Geology 

It was evident that these strata were everywhere plicated and folded, 
and that the observer passed over a repetition of beds, instead of a suc- 
cession of beds; but that the strata, througliout the whole region, had 
been so sliattered by earthquakes, and so metamorphosed, by direct or 
transmitted heat, that it was impossible to identify them, except over 
limited areas." Later, attention was called to the point that this con- 
tinent was as old as the European, if not older.* The above points 
were given in much greater detail in Messrs. Foster and Whitney's 
'4!eport on tlie Geology of the Lake Superior Land District. Part IL 
The Iron Region, together with the General Geology." Transmitted 
November 12, i851.t Such portions of this report as it is necessary to 
note will bo touched upon below. 

Tlie range of quartzose hills extending from Carp River by Teal Lake 
was described to some extent, and was regarded as formed from a 
metamorphosed sandstone. Enclosed fragments of jasper and slate, 
lines of bedding, and obscure traces of ripple-marks were said to have 
been seen in this quartzite (/. c, pp. 15, IG). Of Presque Isle they 
said : "The outline of this mass is very irregular, and resembles an im~ 

* Same Proceedings, page 151. See akso entire article, pp. 13G-151. 
t Senate Documcnty, Spec. So.^s. 32a Cong., III., 1851. 




mense consolidated lava stream, except that the vesicular structure is 
wanting. To the north, the surface of the igneous rock is bare ; but, 
on the eastern side, it is covered in places with a rudely stratified mass, 
which appears to have been deposited in the inequalities of the pre- 
existing surface. It resembles a volcanic sand, or ash, portions of it 
being composed of a scoriaccous mass of a light-brown color, and reticu- 
lated with numerous veins of a white mineral, portions of wliich are cal- 
careous, and others silicious." {l. c, pp. 121, 122; see, also, pp. 18 

and 92.) 

This rock was thought to be of prior origin to the sandstone. Tlie 
sandstone was regarded as Potsdam, and as the same rock as that 
on Keweenaw Point. It was pointed out that this sandstone rests 
nearly horizontally on the water-worn edges of the nearly vertical 
quartzite. {l. c, pp. 122, 123.) The iron ores were regarded as of 
igneous origin, forming intrusive masses and overflows, principally the 
latter, like a lava, but consolidated under pressure of a deep ocean. 
Sublimations of the iron occurred while the denudation and deposition 
of the eruptive masses that Averc by the shore-line aided in making the 
diffeixnt formations. After this series of igneous and aqueous ore- 
beds were laid down, "the whole series of beds, slaty, quartzose, ferru- 
ginous and trappean, were elevated, and, in all probability, folded, per- 
haps at the epoch of the elevation of the granite ranges on the north 
and south of the ferriferous belt of the azoic system." (/. c, pp. 


Dr. J. J. Bigsby regarded the granite as igneous, and taught that the 
metamorphic rocks had been ''upheaved and altered by the intrusion 
of igneous rocks in instances innumerable." t Professor AAHutney, in his 
"Metallic Wealth of the United States," (Philadelphia, 1854,) again ad- 
vocated the igneous origin of the iron ores in this district, as well as iu 

some other localities. t 

In 1854 there was published by Henry R. Schoolcraft, in Philadelphia, 
a work entitled " Summary Narrative of an Exploratory Expedition to the 
Sources of the Mississippi Piver, in 1820 : resumed and completed by the 
Discovery of its Origin in Itasca Lake, in 1832. By Authority of the 
United States. With Appendices, comprising the Original Eeport on 

* Am. Jour. Sci., (2,) XVII. 11-38, 1854 ; XXII. 305-314. 

t Edinburgh New Phil. Jour., 1852, LIII. 55-62. 

X Pp. 37. 429-437, 177, 478. See also Proc. Am. Assoc. Adv. 
209-216; Mining Magaziue, (Now York, 185G,) VII. 67-73; Am. 
(2,) 1856, XXil. 38-44. 

S.^i., 1855, 
Juur. Sci., 





the Copper Mines of Lake Superior, and Observations on the Geology 
of the Lake Basins and the Summit of the Mississippi; together with 
all the Official Reports and Scientific Papers of both Expeditions." As 
giving us an insight into the early knowledge of the geology of tlio 
southern shore of Lake Superior, this woi'k naturally should be of great 
value, especially as it purports to contain the original scientific repoi'ts. 
In the Preface we Icaru that he brings the subject down to the date 
of publication in some respects, and by comparing the work with the 
original, published in 1821, we find that he gives discoveries as if made 
by himself in 1820 wliich were not made until at least nearly twenty-five 
years later. Tliis insertion in the body of the text may perhaps be par- 
doned, in the light of the Preface ; but when it comes to pubhshing offi- 
cial documents with their original date and official signature, but with 
a " tinkered " body, we object. We cannot therefore credit Mr. School- 
craft with the discovery of the iron ore of the Marquette district in 
1820, although any one reading this work would suppose that ho dis- 
covered it. It repi-esents to us simply what he wished, in 1854, others 
shoidd think he had known and written in 1820. This also applies in 
part to his reports on the Copper district, and we shall not mention the 
book further. 

In 1854 was also published a description of this and the Copper region 
by Fr. C. L. Koch,* The trap and granite were regarded as, eruptive, 
and it was thought that the quartz rock (quartzite) may probably be so. 
The schists are supposed to have been metamorphosed through the 
agency of igneous masses. The iron rocks he would consider as 
upheaved from great depths, or else to have suffered great motamor- 
phism by the influence of igneous masses. That they (the iron rocks) 
maybe simply the quartz rock impregnated with oxide of iron is thought 


In 1855 and 185G two papers on this and the Copper district were 
published by Prof. L, E. Rivot.t As wo understand his work, it would 
seem that he regarded all the rocks from Sault St. Marie to the Onto- 
nagon Piver as of sedimentary origin, and of the same geological age, 
whose differences were entirely owing to peculiar metamorphism, or its 
absence, as the case might bo. The sandstones were in general, in the 
Marquette district, of prior deposition to the other rocks in the places 
in which they are now to be found. The traps and their associated 
schists, which originally formed the base of the sandstone, had been 

* Studion des Gott. Vorcins Bcrgni. Frennde, VI. 1 - 248. 
t Aimales des Minos, (5,) Vll. 173-323, X. 3G5-474. 



locally changed and pushed up, dislocating the surrounding sandstones. 
The granites and sienites were regarded as probably the products of the 
last stage of mctamorphism, although they were eruptive in their pres- 
ent position. The *'diorites" of the Marquette district were considered 
to be the same, in age and general characters, as the traps in the Copper 
district, all being interstratificd with the sedimentary rocks with which 
they arc associated, and into which they gradually pass. The differ- 
ences between them and their associated rocks were owing to the degree 
and manner of the metamorphism. The whole formation from the Sault 
to the Ontonagon was regarded as Potsdam, being overlaid by the 
magnesian limestone. 

Prof. J. P. Lesley, in his "Iron Manufacturers' Guide," (New York, 
1859,) opposes the view of Professor Whitney, that the iron ores of 
Lake Superior or of any other region are eruptive. It seems strange 
that a geologist and mining engineer of his reputation should fail 
into the errors that he has, in interpreting the latter's work. After 
quoting Profes.sor Whitney's remarks on mineral veins, he says : " The 
first theory which Mr. Whitney so summarily dismisses as opposed 
to all known facts, is in certain principal localities the only one which 
apparently embraces all the facts. The so-called veins of specular and 
magnetic ore in Northern New York, New Jersey, and Missouri arc of 
this class, and when Mr. Whitney says that *thc mountain masses of 
Missouri have pre-eminently an eruptive character, and are associated 
with rocks which have always been considered as of unmistakably erup- 
tive origin,' we must interpret the expression by the preceding and suc- 
ceeding paragraphs as the judgment of the past, and not his own, saying 
that the specular and magnetic ores of Lake Superior, New York, and 
Scandinavia fall into the same category, and yet are not true veins, but 
'slaty beds impregnated with peroxide of iron, .... exhibiting the 
appearance of a secondary action having taken place since their original 
formation.'" [l. c, pp. 354, 355.) 

On referring to Professor Whitney's work, it can bo readily seen that 
the remarks on mineral veins by Professor Whitney have nothing what- 
soever to do with the above quoted iron-ore deposits, which arc not 
mineral veins in any sense, and were distinctly separated from them by 
him. The expression, *' slaty beds, impregnated with peroxide of iron," 
was used in refc»-cnce to the mine of Hcssel, Norway, while the statement, 
" exhibiting the appearance of a secondary action having taken place since 
their original formation," was applied to the azoic ores of New York, and 
ia copied by Professor Lesley on page 357 of his work in its proper con- 



nection. It will thus be seen that specials have been transformed by 
Professor Lesley into generals, entirely out of their original use ; and 
remarks about one thing are said to have been made about another. 

After copying several pages from Professor Whitnej's "Metallic 
Wealth/' he writes : "It appears from the foregoing that Mr. Whitney 
accepts both the eruptive and the sedimentary theories of the formation of 
the primary iron ores, and applies the former to unknown, inVisible masses, 
antecedent to and now deeply buried under all, even the oldest rocks 
which appear upon the present sm^ffice ; masses of far gi-eater size and depth 
than the greatest yet discovered, proportionate to the greater scale of all 
volcanic action in that prc-azoic day, and offering their sides and tops to 
such erosion and solution as would of course happen in such unsettled 
times, and be sufficient for producing the vast sediments of iron which 
have been taken for volcanic outbursts of the molten metal. But there 
is a fatal difficulty in tiie way of this hypothesis. These ore-beds are 
not breccias. Deposits of the kind imagined would he conglomeritic ; 
blocks of pig-iron would be seen scattered through strata of granite.'* 
Here, again, he has entirely misunderstood Professor Whitney's views, 
which wore that the great masses of ore in tlie Lake Superior district were 
eruptive where they now are, and were never sedimentary deposits, 
while associated with and derived from tliem are the hrecciated and con^ 
glojiicritlc ores, as well as other sedimentary beds. If it is necessary, the 
"pig4ron " can doubtless be found at Ovifak, Disko, in the basalt {I c 
pp. 333-335, 353-361,480-489). 

In 1861 the rocks of the Marquette iron district were referred to the 
Huronian system by Dr. T. Sterry Hunt, on the authority of Mr. Alex- 
ander Murray.* Dr. Hunt regarded the Huronian then as tlic equiva- 
lent of the Cambrian of the European geologists. 

Dr. Danat states concerning the iron ore of Michigan and elsewhere : 
"Their alternation with chloritic and other schists and gneissoid rocks 
shows that they arc metamorphic as well as the schists.'* The same 
statement is made in the edition of 1874 (p. 74), and doubt is expressed 
as to whether they belong to the Laurentian or Huronian (i>p. 151, 152, 
159, IGO). Since the above was written the third edition of the Manual 
has been published, but this affirms as strongly as ever that the iron 
ore is in stratiffed sedimentary beds, and that it is distinctly interstrati- 
fied with the schists. 

* Am. Jour. Sci., 1861, (2,) XXXI. 392-414; Canadian Nat and Geol., 1861. 
VL 81-105, Vn. 127. 

t Manual of Geology, 1862, pp. 83, 84. 



Later, Dr. J. J. Blgsby, while considering the Huronian as distinct 
from the Cambrian, still referred the rocks of this district to the Hu- 

In the "Geology of Canada," 1863, these roci^s are taken as Huro- 
nian (p. (jG). The rock at Presquc Isle was classed as a sedimentary 
serpentine belonging to this formation by Dr. Hunt (pp. 472, 5^5); 
taking his analysis-from Professor Whitney's work,t who regarded it as 

closely related to serpentine. 

Dr. Hunt states also that the great beds of red hematite are strati- 
fied (p. 596), and he considers their deposition as proof of the presence 
of vast amounts of organic matter at that day (p. 573). 

Dr. J. P. Kimball, under date of December 19, 1864,+ remarks : '' My 
own observations in the Iron region impressing me with the indigenous 
character of the larger masses of diorite and granite represented within 
the defined area of the mctamorphic strata, and their entire distinctness 
from intrusive dikes or erupted masses, and concurring in the recog- 
nition of these strata by Mr. Murray as Huronian, I am disposed to 
regard the entire region as of mctamorphic character, all of whose larger 
masses of crystalline rocks are indigenous, and to be divisible into the 
two formations, Laurcntian and Huronian : the former formation proba- 
bly forming the surface of the areas known as the granite ranges, while 
the latter probably occupies, with minor deviations, the limits laid 
down for the crystalline schists comprehended under the name Azoic." 
(L c, p. 293.) "Possessing the same stratigraphical conditions as the 
schistose rocks, while many varieties of them are represented in the 
schists by their exact counterpart as to composition, the crystalline 
Huronian rocks must be regarded as essentially metamorpliic, while in a 
comprehensive view of the whole series it is seen that together with 
variable conditions of deposit, it indicates variable degrees of local meta- 
morphlsm. Plentiful evidence exists of the blending of a rock of one 
character into that of the other, or the continuity between crystallized 
and schistose beds Besides the indigenous crystalline rocks dis- 
tributed throughout the Huronian series, exotic or intrusive crystalline 
rocks are met with, but only in the form of diltes, and limited to a nar- 
row distribution." (I. c, p. 295.) " It may not be inappropriate to 
suggest the probability that the larger and more persistent bodies of 
greenstone bearing approximately east and west — that is, conformably 

* Quart. Jour. Gcol. Son., 1863, XIX. 36- 
t Am. Jour. Sci.,,(2,) XXVIII. 18, 1859. 
t Am. Jour. Sci., (2,) 1865, XXIX., 290- 





■with tlic axes of the folds Avhich constitute a regular system of flexures 
coextensive with the distribution of the Iluronian series in the vicinity 
of JMarquettGj are, in reaHty, indigenous greenstone, and a portion of tho 
development of the diorito upon which repose tlie npper members of the 
Series, and which, as will hereafter be shown, is uncovered along most of the 

ridges of the region." (/. c, p. 21)G.) 

(( T 

The position of the beds of specu- 
lar iron ore has already been stated to be at the top of the Hnronian series, 
.... intcrstratificd with talcose and argillaceous schists. Sharing the 
plications of tlie entire series, these specular schists, as they may prop- 
erly be called, are accordingly folded into synclinal basins and anticlinal 
crests." (/. c, p. 21)9.) " It has been shown that the iron ores of the Hu- 
ronian series in Michigan arc essentially schists and heavy-bedded strata, 
in which none of the phenomena of aqueous deposits formed by precipita- 
tion from water on the one hand, or by dctrital accumulation on the 
other, arc wanting. They exhibit not only stratification, anticlinal and 
synclinal folds, but are invarial)ly traversed by systems of joints, and at 
many points exhibit a perfect slat}^ cleavage. The intimate connection 
between tho grceubtones, hornblende rocks, and aluminous and magne- 
sian silicatcd schists of the ferriferous series, has already been indicated 
in general terms, these rocks not only alternating with, but passing into 
each other." (/. c, p. 302.) *' Chemical reactions in crystalline sedi- 
ments resulting from the disintegration of crystalline silicatcd rocks, and 
operated upon by carbonated waters, are amply capable to have pro 
dnccd the lithological conditions of augitic rocks, clay-slates, schalstone, 
and other schists, together witli the oxidized ores of iron intercalated 
with greenstone among the ancient crystalline rocks of Nortli America 

as well as of Europe From a stratigraphical point of view, while 

evidence is elsewhere often obscure, the Hnronian greenstone, schists, 
and iron ores of Northern Micliigan, in the absence of close attention to 
their special chemical conditions, exhibit sedimentary and metamorphic 
phenomena adequate to render quite untenable, it is believed, tho theory 
of the exotic character of any portion of them." (I.e., p. o03.) The 
granite is also regarded as indigenous by Dr. Kimball. 

Mr. J. W. Foster, in 180-3,* states: "The Iron Eegion consists 
of an assemblage of rocks of various kinds, sucii as argillite, talcose, 
chlorite, and hornhlcnde schists, quartzites, and occasionally dolomites, 
all of which are supposed to be of metamorphic origin, intermingled 
•^dth rocks whose igneous origin can hardly be doubted, consisting of the 

* Geology and Metallurn;y of the Iron Ores of Lake Superior, by J. W. Foster 
and J. r. KinikiU, New York. 



various compounds of feldspar and hornblende, forming greenstone or 
dolorite; or where silica abounds, forming syenite; or serpentine where 

magnesia is in excess It may be stated as a general rule, that 

the great iron deposits of the district occur in close proximity to the 
igneous rocks, mainly greenstone. This roclc forms nearly all of the 
prominent peaks of the region, not in continuous ranges, but in a suc- 
cession of dome-shaped knobs, while the iron ores repose upon their 
sides, or dip beneath their bases, so that the greenstone appears rather 
in the form of intercalated beds than as wedge-shaped masses. The 
^vhole region has been subjected to a powerful denudation, and the 
greenstone, being the more unyielding rock, has been left in the form 
of knobs, or of ill-defined ridges. I cannot recall an instance where it 
forms a true axis of elevation." {L c, p. 9.) The limonitic ores (soft 
hematites of the miners) are regarded by him and by Dr. Kimball as 
formed by the decomposition of the hematite ores in situ {I. c, pp. 24, 
81). Dr. Kimball also states in this report (p. 87): " Kegarding the 
bodies of specular iron ores and earthy red luxmatites of the Marquette 
Kegion as of combined aqueous and metamorphic origin; and, condi- 
tional to this view, apprehending the stratigraphic arrangement of the 
general system of aluminous and maguesian silicated schists, among 
which these beds are intercalated, generally regular and constant as it 
is, the topography of the country affords tangible data for tracing the 
hidden conditions of ore beds, and their relation to outcropping rocks. 
The region is traversed by a series of folds, or undulations, of the entu-e 
series of rocks, which impart to the surflicc its contour, modified only 
through subsequent agencies of denudation. Thus the crests of the 
undulations {i. c, the ridges and hills), originally overlaid by beds of 
iron ore, which in its purer conditions readily yielded to the abrasion 
of glacial action, were worn down and commoidy stripped to the under- 
lying rock." 

In '^ Coal, Iron, and Oil, or the Practical American Miner,'* etc., by 
S. H. Daddow and Benjamin Bannan, published in 18GG, a decidedly 
original view of the origin of the iron ores and their associated rocks, as 
well as of the placer gold of California, is given (pp. 532, 533, 546-550). 
All are thought to have been formed by volcanic action. "We are 
aware that all our sedimentary rocks were formed in water, and that 
the materials forming them are the results of volcanic action. The 
logical sequence is, that those volcanoes cither existed in water, or 
vented their lava uito it. Metals are always heavier than their matrix, 
or the carthv strata in which they are found ; thus, if the lava con^ 









tamed a large amount of metal, it would bo the first to bo precipitated 
to the bottom of the water into which the lava was veuted. The lava 
would not run in a solid stream from the crater, and solidify as a stratum 
in the water, but the moment it touched the adverse element it would 
be shivered to atoms, and thrown back into the atmosphere witli the 
steam it would create, and the lighter portions would naturally arise in 
dust and ashes, and be carried by winds and waves and tides to remo;-^ 
loealities, while the heavier materials would bo precipitated in the 

vicuuty in the order of their density We may refer most of our 

great Azoic bods of magnetic and specular ores aud red oxides of iron to 
this cause, and their formation to these agouoics. We may also refer 
the alluvial or drift gold in the ' placers ' of California and the ' diggin-'s ' 
of Australia to the same causes." (?. c, p. 533.) "^ ° 

It is such theories as this, and many others touched upon in this 
paper, that give the "funny side" to our work, and serve to enliven 
the tedium of it ; otherwise they would not be worthy of preservation 
They stand as the caricatures of science, although they were evidently 
sober realities to their authors. 

A series of papers was published by Dr. Hermann Credner in 18G8- 
70, the titles of which will be given in the literature at the end of this 
work. He divides the formations as ' follows : the gneiss-graultc, or 
Laurentian formation, and the limestonc-quartzite-iron-stone, or Huro- 
mau formation. The latter is sai.l to unconformably overlie the former 
but the evidence, so far as given, is derived from the dip and strike of 
the lamination, and not from observation of the kind and manner of 
their contact. The diorites, iron ores, and all their associated rocks 
except a few, are regarded as interbedded formations. The iron ore is 
supposed to have all originally been m.agnetite, and in part ehano-ed 
since to hematite and limonite. Near Marquette certain diorites were 
seen by hnn to be eruptive ; therefore they were taken to be of differ- 
ent ago from the interbedded diorites associated with the iron ore and 
younger than the Huronian. ' 

In Prof. A. Winchell's ]{eport of Progress of the Geological Survey 
for 18/0 we find the following remark : " The rich masses of ma-nctic 
and hematitie ores of iron are found not to be those erupted outbursts 
which the older geologists were inclined to regard them. They are 
simply constituents of the system -if sedimentary deposits which make 
up the Huronian System of Michigan. The diorites of the region appear 
to be equally of sedimentary origin, and are found strictly interstratified 
with chlontic, siliceous, talcose, argillaceous, micaceous, and hematitie 

VOL. VII, — NO. 1. 




schists, in the foldings and convolutions to which these masses of ancient 
strata have been subjected." {L c, pp. 2G, 27.) 

In 1873 the Report of Major T. 13. Brooks on the Iron districts of 
Michigan was published, with various accompanying documents by 
Messrs. Julien, Wright, Houghton, Lawton, and otliers.* Mr. Brooks 
refers the date of the discovery of the iron ore to 1844, by Mr. Wil- 
liam A. Burt and party, but the first official documents giving an 
account of the ore seem to have been the reports of Burt and Hubbard 
for 1845,t referred to in the early portion of this paper. Besides the 
sandstone, the formations of this district are divided by Mr. Brooks as 
follows : ** The Iron-hearing Each, corresponding, it is assumed, with the 
Huronian system of Canada, consist of a series of extensively folded beds 
of diorite, quartzite, chloritic schists, clay, and mica slates, and graphi- 
tic shales, among which are intercalated extensive beds of several varie- 
ties of iron ore The Granitic Each, which so far have produced 

no useful minerals, and which are believed to be the equivalents of the 

Laurentian of Canada." (/. c, p. 06.) 

As wc shall have largely to deal with Mr. Brooks's work hereafter, wo 
shall quote quite fully from it. '' Useful minerals which occur in beds, 
like the iron ores of Lake Superior, will usually be overlaid and under- 
laid by rocks having different characters, and which maintain those 
characters for considerable distances. Next to finding the ore itself, it 
is desirable to find the hanging or footwall rock. Whoever identifies 
the upper quartzite in the Marquette region, or the upper marble m tho 
Menominee region, has a sure key to the discovery of any ore that may 
exist in the vicinity. With few exceptions, all the rocks in the region 
wc are describing are stratified,- that is, arranged in more or less regu- 
lar beds or layers, which are sometimes horizontal, bat usually highly 
inclined. This stratification, or hedcUvf/, is generally indicated by a 
difference in color of the several layers, oftentimes by a difi^crcnce m 
tlie material itself, but occasionally the only difierence is in the texture 
or size and arrangement of the minerals making up the rock. .... Tn 
general, a striped rock, whether the stripes be broad or narrow, plain or 
obscure, on fresh fracture or weathered surface, is a stratified rock." 

We would invite Mr. Brooks to inspect the volcanic rhyolites, many 
of the felsites that are known to be eruptive, as well as many of the 
furnace slags to be seen in the Marquette district. '^Sometimes the 
power which produced the folds seemed greater than the rocks could 

* Geological Survey of Micliigan, I. 1 -319 ; II. 298 pp. 
t I. 13, 14; II. 235-238. 



bear, and cracks or breaks, tind faults or throws, are the result, though 
these are not numerous in the Lake Superior region. Cracks so pro- 
duced, and iilicd with material other than tliat constituting the adjacent 
rocks, are called d^kes ; or, if the material bo crystalline and metalhf- 
erous, vei7is. As iron ore in workable quantities docs not occur in this 
form in this region, vein phenomena will not be considered here." Of 
the Iluronian scries "the prevailing rock is a greenstone, or diorite, in 
which, like the copper traps, the bedding Is usually obscure ; but the 
intercalated schists and slates, which usually bear strong marks of strati- 
fication, make it usually not difficult to determine the dip of the beds 
at auy point. . . . Descending to the oldest or bottom rocks of the 
Lake Superior coimtry, the granites and associated beds (Laurentian), 
wo find the bedding indications still more obscure, and often entirely 
wanting." {I. c, pp. 74, 75, 7G.) 

" In subdividing the Ilui'onian or iron-bearing series which we have 
particularly to study, the rocks have been grouped (1) lltkologically , i, e., 
according to their mineral composition, and (2) stratiyraphically, L <-., ac- 
cording to relative age. As this system was first described and named 
by the Canadian geologists, their namcfe have been employed as far as pos- 
sible in the body of this report; the identity in composition of many of 
our rocks with theirs, having been established by an examination of a large 
number of Marquette specimens by Dr. T. Sterry Hunt." (/. c, p. 82^) 

u fp 

The several beds or layers of the Iluronian system, as developed in tlie 

I\rarquctte region, are nuinbcred upwards from I. to XLX L, IT., 

IIL, ly., are composed of beds of siliceous ferruginous schist, alternating 
with chloritic schists and dioritcs, the relations of which have not been 
fully made out; V. is a quartzite, sometimes containing marble and 
beds of argillite and novaculite ; VL, VIIL and X. are siliceous fer- 
ruginous schists; VTL, LX. and XL arc dioritic rocks, varying mucli 
in character; XI FL is the bed which contains all the rich specular and 
magnetic ore, associated with mixed ore and magnesian schist; XIY. is 
a quartzite, often conglomeritic ; XV. is argillite or clay slate ; XVL is 
uncertain, it contains some soft hcuiatite ; XVII. is anthophyllitic schist, 
containing iron and manganese; XVIIL is doubtful ; XIX. is mica 
schist, ^containing stanrolite, audalu^ite, and garnets. This classifica- 
tion, it will be borne in mind, applies oidy to the Marquette region. 
. These beds a])pcar to be metamorphosed sedimentary strata, havin- 

« * # 


many folds or corrugations, thereby forming in the Marquette region an 

irregidar trough or basin Wliile some of the beds pi-escnt litho- 

loglcal characters so constant, that they can be identified wherever seen 




others undergo great changes. Marble passes into quartzite, which in 
turn graduates into novacuhte ; diorites, almost porphyritic, are the 
equivalents of soft magnesian schists." (/. c, pp. 83, Si.) 

The '* soft hematites " are thought to result, perhaps, from the decom- 
position of a 'Himonitic siliceous schist," with which they are associated. 
*'It is not at all improbable that this change may have been brought 
al)out by the alkaline waters of former thermal springs." (/. c, pp. 

90, 91.) 

The ''diorites" arc said to graduate from a heavy, tongh, black 
variety into a soft, light-colored rock, resembling chloritic schist more 
tlian anything else, and called by him dioritic schist. *' The bed- 
ding of these rocks is generally obscure, and in the granular varieties 
entirely wanting. It is usually only after a full study of the rock in 
mass, and after its relations with the under and overlaying beds are 
fully made out, that one becomes convinced, whatever its origin, it 
presents in mass precisely the same phenomenon, as regards stratifica- 
tion, as do the accompanying schists and quartzites No reference 

is here made to tlie false stratification or joints, which are numerous and 
interesting, but which unfortunately, for want of space, can receive no 
other attention here than to warn the observer against mistaking j/V/^V^ 
planes for heddlng planes, which is sometimes done, even by experienced 
observers." (/. c, pp. 102, 103.) lie also states that in no case has he 
abserved a Huronian diorite in the Marquette district that does not con- 
form " with the schistose and slaty strata with which they are associ- 
ated." (/. c, p. 15G.) 

The rocks associated with the hard ores and ''diorites" are called 

''magnesian schists (mostly chloritic)." lie says regarding them : *' It 
would be difficult for a skilled lithologist, and impossible for me, to draw 
the line between the chloritic schists here considered and the dioritic 
schists." Regarding the chloritic schist at one locality associated with 
''specular slate ore," it is stated : " Prof. Tumpelly has suggested that one 
may be a pscudomorph after the otlier. In this comiection it may bo 
remarked that no gradual transition of one into the other was observed, 
the division planes being in each instance sharply defined." Q. c, pp. 
104, 105.) 

Eegarding the connections of the ore in the Larnum nunc with that 
in the Lake Superior mine, he writes : "It shows that such formations 
are not vein or dyke-line deposits, but true stratified beds, like the 
rocks by which they arc enclosed. Their structure is therefore essen- 
tially the same as the coal, limestone, sandstone, and slate-beds, which 





are regarded as sedimentary deposits from water, subsequently more or 
less altered by beat, pressure, and cbcmical waters acting during im- 
mense periods of time. Tbe Lake Superior-Barnum deposit evid^ently 
has a bottom, which will be reached within a period, of which it is worth 

while for the present generation to take some heed The time 

may come when, havnig worked out the steep, upturned edges of the 
basins, and the flatter or deeper portions of the deposit arc reached, ore 
properties will be valued somewhat according to the number of acres 
underlaid hj ore, as coal now is. Passing to the east portion of the Lake 
Superior mine, I confess myself unable to give any intelligent hypothe- 
sis of its structure There seems to have been such a gathering 

together, crumpling, squeezing, and breaking of the strata, as nearly to 

obHterate the stratification The remarkable features are the 

great masses of light grayish-green chloritic schist, having a vertical 
east and west cleavage, no discernible bedding planes, and liolding small 
lenticular masses of specular ore, which conform in their strike and dip 
with this cleavage, and which seem to have no structural connection 
with the main deposits. They appear like dykes of ore, squeezed out of 
the parent mass, which we may suppose t*o have been in a comparatively 
plastic state when the folding took place; or they may have been small 
beds, contained originally in the chloritic schist, and brought to their 
present form and position by the same causes, which produce the cleav- 
age in the schist Thepeculiar nature of the hanging wall of the 

Lake Superior mine deserves further notice. Instead of the quartzite, 
whicii we have hitjierto found overlying all the deposits of rich ore, we 
have here a magnesian schist very similar to, if not identical with, that 
already mentioned as being associated with the ore." (/. c, pp. 138 - 140.) 
"AH the Iluronian rocks north, east, and south from the Jackson 
mine are below, or older than the ore format Urn (XllI)., and all the 
rocks to the westward and inaiile of the ore-basin are youncjer, hence 
above it." (/. c, p. 143.) '*The iron-bearing or Iluronian series of rocks 
are stratified beds, the principal ore formation being overlaid by a 
quartzite XIV., and underlaid by a diorite, or greenstone XI. This^ire 
formation is made up, first, of pure ore; second, of 'mixed ore' (?'. e. 
banded jasper and ore); and third, a soft, greenish schistose, or slaiy 
rock (magnesian), wliich occurs in lens-shaped beds which alternate witli 
ore, tlms often dividing the formation into two or more beds of ore. sepa- 
rated by rock. Usually the beds of both ore and rock thin out as they 
arc followed in the direction of the strike from a centre of maximum 
thicluiess, producing irregular, lentiform masses. Since their ori-inal 



regarded one of the rocks at least. 

deposition, if we may assume tliey were laid down imdcr water, the 
whole scries, including the iron beds, have been bent, folded, and cor- 
rugated into irregular troughs, basins, and domes, which often present 
at the surface their nj^turned edges of pure ore, standing nearly 
vertical." {I. c, p. 245.) "The tronble is to End out when a pit is 
exhausted, — it is so common to break through a thin layer of rock, and 
find a bed of workable ore behind it." (/. c, p. 262.) 

The proof advanced by Mr. Brooks to show the unconformability of 
the so-called Huronian to the so-called Laurentian, and the greater age 
of the latter, is in substance this : the foliation of the latter was found 
in two places to dip in a different direction from that of the lamination of 
the "Huronian" schists nearby {l. c, pp. 12G, 156). His proof then 
rests entirely on the hypothesis that these planes are the original bedding 
planes of these rocks. This hypothesis again assumes that all are sedi- 
mentary rocks, — a point still in doubt at the time of his writing, as 

It is to be noticed that the two 
formations were not seen in contact. He also remarks (/. c, p. 156) : 
"The non-conformability is further proven by the fact that the Lanren- 
tian generally abounds in dikes of granite and dioritc, which are almost 
entirely absent from the Huronian;* Concerning certain rocks in the 
Menominee district we find this acknowledgment : " It must be ad- 
mitted, however, that the lithological affniities of this scries of rocks 
of the north belt are decidedly Laurentian, rather than Huronian. The 
gneiss and granite outcrop above described, may be almost regarded as 
a typical Laurentian rock in its appearance. If future investigations 
prove them •to be Laurentian, a very troublesome structural problem 
would be presented here, as wo wonld have Lanrentian rocks conform- 
ably ovcrhjlng beds, nnmistakably Huronian. There seem to be fewer 
difficulties in supposing that the Huronian rocks of the Menominee 
region embrace lithological families not, so far, found represented in 
tlie equivalent series in the Marquette region." (/. c, p. 175.) 

Part III. of the above-mentioned work is devoted to tlio report of Dr. 
C. Ilominger. We take some extracts from this : "A locality on the 
shore, two miles south of Marquette, where the sandstones in their con- 
tact with the Huronian Quartzitcs can be seen, has been previously de- 
scribed in Foster and Whitney's report on the Lake Superior district. 
W^e find here vertically erected white Quartzite beds of the Huronian 
group projecting into the lake, which have preserved their graimlar sand- 
stone structure, and are distinctly ripplc-markcd. Tlicy are snrrouiuled 
by brown sandstone and conglomerate ledges, horizontally abuttnig 



againsf them. The sandstones, wliicli arc of very irregular discordant 
stratification, closely adapt thoniselves to all inequalities of the cliffs, 
which exhibit under the sandstone covering a rounded water-worn sur- 
face, indicating their long exposure before they were enveloped by tlie 
sandstones." (/. c, p. 90.) 

Of Presque Isle he says: '^ This landspur is formed by a protrusion 
of peculiar rock^masses, differing considerably from the rock-beds of 
the Huronian group in the vicinity. Lowest is a black, nnstratified, 
serai-crystalline magnesiau rock, resembling a half-decomposed basalt 
or a highly ferruginous serpentine. It forms considerable cliffs at the 
north end of the spur; — more to the south we find it overlaid by a 
more light-colored, oncc-stratilied rock, which is involved in the up- 
heaval, with its ledges bent and broken up in great confusion.'' llo 
regards this as a dolomite. It is the same rock that Houghton consid- 
ered to be sedimentary, and Foster and Whitney as a volcanic ash. 
*'0n the south portion of Presque Isle this dolomite is iuconformably 
overlaid by a conglomerate and succeeding sandstone layers, which are 
identical with the sandstones of the Marquette quarries. The sand- 
stone strata some distance off from the protrusive rocks arc nearly hori- 
zontal.* In innnediate contact with them' they have a considerable dip, 
corresponding to the convexity of the underlying surface. It is pos- 
sil)le that the strata were slightly uplifted after their deposition, but 
I am more inclined to explain the existing dip as an adaptation of tho 
sediments to the surface on which they wore deposited. The conglom- 
erate beds at the base arc five feet thick, and contain numerous Ifrag- 
ments of the underlying dolomitic I'ock and of their enclosed Jaspery 
minerals." {L c, pp. 90, 91) Pie regards certain rocks at Lightdiouso 
Point and Picnic Island as intrusive diorites, giving evidence therefor, 
and also remarks: *' The Diorites inter stratified with the Huronian 
schistose rocks in the environs of Marquette, and particularly at the 
Light-house point, are of an evidently intrusive character." (L c, p. 
93.) The italics arc ours, as we are anxious to know how the same 
rock can be interstratificd and intrusive at the same point.* 

In a paper by Prof J. S. Newberry, on - The Iron Resources of the 
United States," t we find the following statement: ** On Lake Superior 

* May we bo pardonod for saying that, accordiii- to Messrs. rumpcUy aud llrooks 
(soe quotations from tlieni on the Cupper district), this is proof positive tliat the Pots- 
dam sandstones abut nnconforjnably iigamst the rrcs(jtce-idian merles, which must 
then have formed an island in the Pot,sd;ini sea. 

t International licview, 1875, I. 754-7S0. 



it is now easy to see that the ore-beds were once horizontal 'strata, 
deposited iu conformity with many other stratified sediments, but they 
are folded and broken in such a way that their true nature was for 
a long while misunderstood. Like the magnetic ores of the Alleghany 
belt, they were once considered eruptive ; but the progress of modern 
science has shown that all the so-called Eozoic iron ores are simply 
metamorphosed strata, once deposited horizontally like the sheets of 
iron ore now found in the unchanged Palaeozoic rocks, —such as the 
Clinton ore and the * black-band' and *clay ironstone' of the Coal 


Col. Chas. Whittlesey,* in 1875, opposed the idea that the granitic 
region was Laurentian, but regarded the rocks as eruptive. He accepted 
the view of the Huronian age of the schists, however. 

In the Transactions of the Wisconsin Academy of Sciences, Arts, and 
Letters,t Mr. K T. Sweet calls attention to the unconformability of tho 
Laurentian and Huronian with one another at Penokic Gap, Wisconsin. 
It will be seen, however, by reference to the paper, that the absolute 

contact was not observed. 

In 1875 Mr. Brooks again took up the question of the granites in the 
Mcnomonee district, which, according to him,J overlie the iron-bearing 
rocks of that region. In order to solve the difficulty he assumes that 
they arc tho youngest Huronian rocks (Formation XX.), and immedi- 
ately underlie the copper-bearing series.§ 

The only reason, so far as we can learn from his paper and the original 
observation quoted by us {ante, page 22), for this supposition is, that, 
while they arc lithologically identical with the '' Laurentian" rocks, he 
can dispose of them best by placing them as the youngest of the Huro- 
nian rocks. Furthermore, unless he did this, the *' Laurentian" would 
be younger than the " Huronian " at this point, a conclusion that would 
vitiate his former statements. He therefore deliberately violates tho 
lithological laws on which his work rests, and makes it simply a ques- 
tion of where each rock will fit into his system the best. 

From Dr. T. Sterry Hunt's ^' A/oic Rocks," || we learn that from hand 
Bpecimcns sent him by Mr. Brooks he established the presence of the 
Montalban series, as well as the Laurentian and Huronian Q, c, p. 









* Proc. Am. Assoc. Adv. Sci., 1875, XXIV. 60 

t Vol. III., 1875-76, pp. 40-55, 

X Mich. Geol. Survt^y, 1. 175. 

§ Am. Jour. Sci., 1876, (3,) XI. 206-211. 

11 Sec. Gcol. Survey of Ten n. E. Tart I. 





223). The greenstones of the Huronian were also said to be indigenous, 
i. c. rocks formed in situ from sediments (/. c, p. 221). 

Wc next come to the report of Mr. Charles E. Wright,* in wliich we 
are informed that all the granites of the Upper Teninsula and Wisconsin 
that have been examined by the writer are metamorphic. This view is 
based upon microscopic cliaraeters, and wo should object, in toto, to tho 
premise. He also states : *' Some objections were made last summer 
(1870) by Dr. Kominger as to the non-conformabiiity of our so-called 
Laurentian and Huronian series, on the ground that he had observed in 
several instances ^ a j^erfcct conformability of these supposed distinct 

It seems perfectly natural to me that this should often occ\ir; 
and were I to find ninety-nine places where an apparent conformability 
existed, and only one of decided non-conformability, the latter would, in 
my estimation, outweigh all the former.'' (/. c, p. 11.) He states that 
a perfect case of nonconformability exists at " Penoka Gap," Wisconsin, 
to which we have before referred; but if we remember correctly Mr! 
Wright's personal statement to us, neither was the junction seen nor 
the kind of junction known that the two made with each other. It is 
too fast to assume, as has been done by Messrs. Brooks, Irving, and 
Wright, that the strike and dip of a foliated rock is the strike and dip 
of its stratification. This is especially the case when the view that they 
were ever stratified is still a disputed point. 

Of the Huronian series the quartzite is said to show frequent ripple- 
marks. The soft hematite is thought to have been formed as follows : 
" In these mines it appears that tho finely divided silica has been more 
or less dissolved out by alkaline thermal water, leaving the iron oxide 
and other bases behind.'' (/. c, p. 15.) The iron ore is regarded as 
sedimentary, and Brooks's geological ideas are closely followed. 

He sustains Mr. Brooks's, division of the granites into Laurentian and 
Huronian (Formation XX.), by tho statement that he finds salt cubes 
in tho fiuidal cavities of the latter, but not in the former. 

Lastly, we have Mr. W. 0. Crosby's paper, '* On a Possible Origin of 
Petrosiliceous B,ocks,"t in which he thinks it probable that the Jasper 
and its associated iron ores are the representatives of a deep-sea deposit, 
like the '' red clay " discovered by the Challenger expedition, below tho 
depth of 2500 fathoms. 

It may not be amiss to incidentally refer to the treatise of Mr. 

* First Annual Report of tho Commissioner of Mineral Statistics for tho State of 
Micliigan, 1879. 

t rroc. Bust. Soc. Nat. Hist., 1879, XX. 160-1G9. 




D. C. Davics on Metalliferous Minerals and Mining.* It would be 
difficult to imagine a deseription or a section so at variance with 
the facts as the ones that he gives on pages 274 and 275. We 
feel that all geologists who have been in this region will be sur- 
prised to be informed that *' lingnl&o are abundant in the overlying 
sandstone." On page 149 he has represented the copper-bearing rocks 
and sandstone (Potsdam) as resting directly upon, and at a steep angle 
dipping away in both directions from^ the iron-bearing rocks ; also, the 
•western copper rocks as dipping cast, and resting upon a similar set of 
iron rocks. It is to be hoped that the rest of his book is not so errone- 
ous as this. 



Historical Summary. 

In general, then, in looking over the views advocated by past ob- 
servers, we find, in brief, the following opinions held. 

The rocksf of this district were all taken as azoic by Poster and 
Whitney, and not considered to be capable of subdivision into geologi- 
cal periods. Wc must also notice that Prof. IT. D. Eogers regarded 
them as of primal or Potsdam age. On the other hand, we find that 
this formation is divided by Murray, Hunt, Kimball, Winchell, Credner, 
Brooks, and Wright into the Iluronian and Laurentian. This division 
is based upon lithological characters, and an unconformability said to 
exist between the two. Eivot considered the whole as Potsdam. 

The granite is regarded as an eruptive rock by Foster and Whitney, 
Bigsby, and Whittlesey ; and as of sedimentary origin by Pivot, Kimball, 
Brooks, Plunt, and Wright. These latter, with Credner, take it as being 
older than the schistose rocks associated with the iron ores, and, except- 
ing Eivot, with its accompanying gncissoid rocks composing the Lauren- 
tian formation. Foster and Whitney and S. W. Hill regarded the gran- 
ite as younger than, and eruptive in, the schists. 

The gneisses and schists were taken by all the observers as being of 
sedimentary origin, except possibly Whittlesey, whose language is as 
obscure as the formations about which he writes. 

The metamorphism of the schists is supposed by Hubbard, Pivot, 
Kimball, Hunt, Brooks, and Wright to be occasioned by chemical agen- 
cies accompanied, as part thought, by galvanism. Foster and Whitney 
and Bigsby considered that the metamorphism was brought about by 

* London : Crosby, Lockwoo(l,& Co., 1880. 

t Excepting tlic sandatonc, which will he spoken of in our remarks on tUc Copper 














the presence of eruptive rocks, and tlicir accompanying chemical agencies. 
Fowter and Whitney regarded the " diorites " of this region as eruptive 
rocks, but lUvot, Kimball, Hunt, Wiuchell, Credner, Brooks, and Wright, 
as sedimentary ones and interstratificd with the scliists. 

The iron ores are regarded as all of sedimentary origin by Foster, 
Kimball, Dana, Hunt, Wiuchell, Crednoi-, Brooks, Newberry, and Wright, 
but are believed for the most part to be of eruptive origin by AVhitney, 
and by Foster and Whitney. These ores were said to be in the upper 
portion of the Huronian series by Kimball, Brooks, and Wright, with the 
" diorites " underlyhig them. 

It will thus be seen that, while Foster and Whitney regarded certain 
of the rocks in the '^luronian " as eruptive, Hubbard, lUvot, Kimball, 
Hunt, Credner, Brooks, and Wright regarded all, with a few slight excep- 
tions, as sedimentary; and Houghton, Hubbard, Locke, Kimball, Eivot, 
and Brooks teach that they pass by gradual transition into one another. 

The most important points, then, about which there has been or is 
diUcreuce of opinion, are the age and relation of the granite and schists, 
the origin of the diorites and iron ores, the passage of one rock into 
another, and the presence or absence of eruptive rocks. These and other 
questions relating to this district admit in many cases of no middle 
ground ; one or the other party must be mistaken in their observations 
or conclusions, or both. All these questions lie closely to the fundamen- 
tal propositions of geology; they reach to the superstructure of the 


Methods of Observation. 

The object of the writer in visiting the Iron district was to clear up 

some of the preceding mooted points in the geology of that region, if 

possible, especially the origin of the iron ores and their relations to the 
country rock. 

From our personal experience in botli regions, we should hold that 
the ordinary methods of geological research which are employed in the 
study of the comparatively undisturbed and unaltered sedimentary 
rocks of the Mississippi Valley are not sufliciently accurate for our pur- 
pose in the Lake Superior district, where the rocks are foliated, dis- 
turbed, and of niixed eruptive and sedimentary origin. Stratigraphical 
laws that hold good in the former region do not in the latter, especially 
wdien it is sought to connect together two rocks of unlike character, or 
when the nature and origin of either or both is a point of dispute. In 
this disturbed district the presence of a rock in one place w'ili hardly 




prove the presence of tbe same one in another, except by direct connec- 
tion, even if the two do look alike, especially if that sameness is ques- 
tioned. If the two rocks are identical in structure and composition, 
nothing but the proof of direct, absolute continuity places the question 
of thei^'r identity beyond dispute here, especially if we have any reason 
to suspect the eruptive origin of one or both of them. Lamination, 
banding, joint planes, cleavage, pseudo-stratification, and fluidal struc- 
ture, are not to be taken as proof of stratification in doubtful rocks. 
The' very origin and nature of all, except, perhaps, the true lluidal 
(not pseudo^fluidal) structure, arc yet open questions. Until it is 
proved that they are confined to one class of rocks, it is unsafe to use 
them to prove that any questionable rock belongs to that class. Doubly 
so is it when it is well known that they are not so confined. If they 
are not to be used to determine the sedimentary origin of a rock, in like 
manner the dip and strike of such structures ought not to be taken to 
prove order of superposition, conformability, or non-conformability, 
especially as this proceeds upon the supposition that both rocks in 
question are sedimentary. That a sedimentary rock is horizontal, or 
has a certain dip at one place, is not to be taken as proof of what its 
position must be in another locality, unless the conditions remain the 


It may be said that every rock carries in itself, or in its relations to 

its associates, or both, its history, more or l^'ss complete. In order 
to read and understand this history, it seems necessary that we should 
be able to distinguish between the fragmcntal and non^fragmcntal 
forms • the characters assumed by a lava flow and its associated 
detritus, their relations to one another and to the over and underlying 
rocks; the characters of an intrusive rock, its effect upon the country 
rock, and the nature and kind of junction that they make with each 
other ; tlic relations that sedimentary rocks have to their over- and 
nnder-lying rocks ; and the alterations to which all classes are subjected. 
One of thc^iost common errors made, is by observers taking the ground 
■ that two outcropphig rocks that look alike are of necessity the same 
geologically, and form a continuous whole, although no direct connection 

is proved. 

It now remains for us to enter upon the questions before us. 

The Jasper and Iron Ore. 

The country rock is of a varying nature, but is mainly composed of 
schists (largely chloritic), argillitcs, and quartzite, in that part of the 









-tv^,— i^^-v^.m 





district visited by us. Associated with these rocks is the jasper, which 
is acknowledged on every hand to be an inseparable part of the iron ore 
formation. The origin of one gives the origin of the other. Their 
interdependence is such, and has been so regarded, that- the relations 
of one to the country rock give the relations of the other. The two 
have been so fully described in the past, that it is only necessary to 
briefly describe them here. 

The connnon form is that of interlaminations of jasper and iron ore, 
the laminte varying from extreme tenuity to considerable thickness. In 
some places the jasper predominates, in others the ore. In the hist case 
we have a more or less valuable ore, according to the amount of the sili- 
ceous material, which, however, may exist only in a mere trace. The 
l)urer parts form large masses, that are mined, and which graduate into 
the jasper, or ore containing so mucls jasper as to be unfit for working. 
The workable parts are frequently lenticular in form, although often 
irregular. The irregularity of the ore mass, its passage into the jaspery 
ores, and the uncertainty where the next mass will be found, are amon(>* 
the chief difficulties of the miner. The origin of the jasper and ore 
becomes then a problem of great economic importance, as do also the 
relations of both to the country rocks. Tlic permanence and extent of 
the formation, whether it is in the form of vein deposits, eruptive (intru- 
sive or overflow) masses, or sedimentary deposits, are questions in which 
the capitalist and minor, whether they Avill or not, are most deeply 
interested. As tliey have never been regarded as vein deposits, there 
remains for us only the question whether the jasper and its associated 
ores are eruptive or sedimentary in origin. 

Lest there be some misunderstanding as to to the reason for thus dis- 
missing the theory of the ores here being vein deposits, we would remark 
that the question has been ably and fully discussed before in the works 
of previous observers. Furthermore, while veins on a small scale are 
occasionally seen, we were unable to find upon cither the jasper or its 
associated ore a single cliaracter belonging citlicr to a vein or an infil- 
tration deposit. It therefore seems unnecessary to discuss the vein or 
infiltration theory here. 

As both the eruptive and sedimentary origin of the jasper and the 
ore have been advocated by some of the most eminent Kcolo^jists in this 


country, it is necessary that the question should be answered by the 
facts, and not by any preconceived theory or idea. The question now is 
what are the flicts, and their most probable explanation. The first and 
most important thing to be observed in deciding this is the relation of 
the jaspery formation to its country rocks. 



This relation is well shown in and about the Lake Superior mine at 
Ishpeming. On the north side of one of the abandoned pits just east of 
the main workings, the junetion of the jasper and ore with the chlorite 
schist was observed and figured. (Fig. 1.) Specimens were also taken that 
show the contact (U3, 144, 145, 14G, and 147) * The junction of the two 
is very irregular, the banding of the jasper and ore following the irregular- 
ities of this line, while the schist is indurated and its laminae bear no rela- 
tion to the line of contact. Stringers of ore project into the schist, which 
near the jasper is filled with octahedrons of magnetite. The scliist loses 
its green color generally, and becomes apparently an indurated argillite. 
The contact and relations of the two rocks are not such as are seen when 
one sedimentary rock is laid down upon another, but rather that observed 
when one rock is intrusive through another; and in this case the intru- 
sive one is the jasper and its associated ore. On the south side of the 
same pit the jasper bows in and out in the schist, forming at one place 
a projecting knob whose banding follows its contour. Lying against it 
is a long arm of jasper, simihirly banded, which ends in a rounded knob. 
This is represented in plan (Fig. 2), and specimen No. 150 was taken 
from the end of the latter projection. In the southwest corner of the 
same pit a dike of very fair hematite ore (155) about one foot in 
width breaks at an angle of 15° across the argillite (154) and schist, 
whose lamination is vertical. (Fig. 3.) Wherever the unbroken con- 
tact of the jasper and ore with the scliist could be observed, that junc- 
tion is seen to be an eruptive one, on the part of the former (15G, 157, 
and 158). At the Schoobhouse mine east of the Lake Superior mine, 
the jasper forms a dike with a knob-like ending, the lamination (band- 
ing) following the curvature of the sides. The contacts between the 
ore and schist were wcU-marked eruptive ones (1G8, 1G9). Overlying 
the ore was found on one side a ferrughious and quartzosc breccia and 
conglomerate composed principally of the ruins of the underlying ore and 
jasper (IGG, 1G7). A similai- but fmer-grained rock, mostly a quartzite, 
forms the hanging, or better the fallen wall of the New York mine. 
This is composed, in like manner, chiefly of the debris of the underly- 
ing ore and jasper. Mr. Brooks's statement regarding the "quartz- 
ite" of the Marquette district (p. 18) is undoubtedly true of this rock, 
that when ho finds the ''quartzite," adjacent to it will be fovuid all that 
is left of the ore formation. This, however, is not what Mr. Brooks 

* The nnrnhers enclosed in marks of parentliesis refer to Kpechncns collected by 
tlic -writer, and depoyitcd in tkc Litliological Collection at the Museum, of Com- 
parative Zoology. 







Inteiulod in his statement, us tlieso dctrital rocks apparently form but 
a small portion of his " qnartzitcs." These of course. mark old beaches 
watcr-woru after the jaypcr and ore were in sUa, in nearly their present 
condition, and, if the logic of the geologists of the Michigan and Wiscon- 
sin surveys were carried out, these unconformable dctrital formations 
■would mark a new geological age. 

One difficulty found in mining the iron ore has arisen from the schist 
being found in large masses, broad at the upper part of the mine, but 
tapering out to thin wedge-shaped masses below, which are left without 
support when the ore is removed. This renders one wall, and some- 
times both, unsafe, no one foreseeing when the support to the treacher- 
ous scliist will be removed. This structure evidently is consonant with 
the tlicory of the eruptive origin of the jasper and ore. They break 
obli(picly up through the schist, and send off branches, which, pursu- 
ing the same general course, leave wedge-shaped masses between them 
and the trunk. The ore when removed allows that which has been 
supported by it to fall. This very cutting across the lamination, how- 
ever sliglitlj^, would tend to let all severed masses slide out, even if 
they were cut on one side only. Figure 4, taken from an actual 
section in an old working at the southeastern end of the Cleveland 
mine, Islipcming, whows the phenomenon very well, and its cause. Tho 
branches of ore are about two to three inches wide here, the main body 
being about twelve inches in thickness, and tho relations can be well 
studied. In several places near this point the irregular wavy line of 
contact between the schist and ore can bo seen; and all bodies of this 
or the jasper were f )und on close examination not to coincide with the 
lamination, liowever nmch they may appear to do so. 

At the upper portion of the Jackson mine, Negauneo, tho jasper and 
hematite were seen to cut across and obliquely up througli the schists. A 
vertical section as shown by the former mining done at this point is given 
in Figure 5. The jasper also curves in a similar manner at right angles to 
this nearly east and west section. While this (the figure, not the actual 
occurrence) could be explained easily by sedimentation, it is fatal to tho 
view of conformable deposition. In pit No. 3 of this mine (Jackson) 
the ore breaks irregularly through the schist, forming a brecciatcd-look- 
ing mass, while in other cases it runs up into the schist ending in irreg- 
ular knobs. Figures G and 7 show some of the occurrences observed 
and figured from the pit walls. Figure 8 represents a section about 
forty feet in height at the west end of No. 7 pit in the same mine. The 
schist sliows bending and dislocation as represented in the curve 6, c, 







which shows the direction and manner of the upthrust. The point a 
is at such an elevation that wc are not able to assort that it is part 
of the same formation. It certainly looked the same, and the assist- 
ant captain in charge of the' pit stated that he knew they were the 
same. The entire mass of jasper and ore represented here had been so 
acted upon by secondary agencies that it had been mined as " soft hema- 
tite." In the same pit a beautiful brecciatcd jasper occurs in which the 
hematite forms the cementing material (269, 270, 271, 272). 

In pit No. 4 a wedge of ore and jasper was seen intruding between 
and across the lamination of the schist. (Fig. 9.) In the " north pit " 
the eruptive character of the ore is well shown; Figures 10, 11, and 12 
showing sections exposed on the walls. Overlying the ore at a low angle 
is a quartzite containing jasper and ore derived from its underlying ore 
(277). At the Home mine in the Cascade range the ore was largely 
a sandstone impregnated with hematite (257), strike N. 70° W. with 
a northerly dip, which varies owing to the contortion of the strata 
from 30° to 70°. Several dikes of jasper run through this sandstone, 
in part conforming to the bending of the strata, .and in part breaking 
across the lamina; (258, 259, 200, 201). Specimen 259 shows well the 
contact between the two rocks, the jasper and sandstone, which contact 
in a less degree is shown by the other specimens. One of these dikes 
is represented by Figure 13, in which the width is exaggerated compared 
with the length. There is no mistaking the intrusive character of the 
jasper and its interlaminated ore here. It is of course almost unneces- 
sary to state that this mine, having as its chief ore a ferruginous sand- 
stone, was long since abandoned. The quartzite (metamorphosed sand- 
stone) which forms the hanging wall of the Pittsbui'g and Lake Superior 
mine, Cascade range, has been cut through by dikes and little stringers 
of nearly pure hematite (202, 203, 204), which in its present position is 
distinctly intrusive. While in general these little dikes follow approxi- 
mately the bedding, they are seen not to exactly do this, but cut the 
lamina obliquely through much of their course. This mine contains as 
a secondary formation much specular iron (205). Near the bridge over 
the Palmer mine the jasper shows well its eruptive character in its junc- 
tion with the quartzite, while the banding is seen to bo parallel to the 
contact line. This jasper holds in it, and as part of itself, the hema- 
tite mined here. 

It is advocated by Messrs. Credner and Brooks that all the iron was 
originally in the state of magnetic oxide, this view being sustained by 
the" crystals of martite found in various parts of the district. 







It would seem that a microscopic examination of the banded jasper 
and ore should give us some facts bearing upon the question. A sec- 
tion was made of a finely-bauded jasper (13G), taken near the Lake 
Superior mine. Under a lens this shows a line contorted banding. 
Microscopically this section is composed of a fine granular aggregate of 
quartz and liematite, and a more coarsely crystallized portion made up 
of octahedrons of magnetite or martite, and of quartz of secondary origin. 
The quartz in the first part is largely tilled with minute globules and 
grains of ore, which also occurs in irregular masses and in octahedrons. 
The quartz associated with the more coarsely crystallized portion is 
water clear, and shows the usual fibrous gramdar polarization of second- 
ary quartz. Wherever the iron is in a distinguishable crystalline form 
it is in octahedrons. The color and streak of the iron in the hand 
specimen are those of hematite, but tlie povvtler is found to be nuignetic. 
No. 153, from the same locality, has similar characters. The section 
was taken from the most jaspery portion, and shows much of the fmo 
aggregation of quartz and hematite. The structure of the quartzose 
portion is like the devitrification structure of the rhyolites anil fclsites. 
The section has been repeatedly fissured, and the fissures filled in with 
secondary deposits of quartz and octahedral crystals of iron. So far as 
we have observed, the brecciated jasper and ore have had their fractures 
filled in like manner. No. 271, from pit No. 7, Jackson mine, is of similar 
character. The jaspery portion is finely banded, and shows an apparent 
fluidal structure. We are inclined to regard the structure as fluidal, 
but in a rock so deeply colored it is difficult to make satisfactory exam- 
inations. This is the only section that shows anything like a well- 
defined limit between the jasper and ore bands, under the microscope, as 
pointed out by Dr. Wichmann.''^ The powder of the two last-desci'ibed 
specimens is feebly magnetic. No. 202 was from the Pittsburg and 
Lake Superior mine, Cascade range. This shows ihe intrusion of the 
iron ore through the quartzite (p. 32). The ore gives the hematite 
streak, is feebly magnetic, and appears to be in octahedrons. The 
quartz is m\ich fissured, shownng the effect of heat, and contains micro- 
lites and fluid and stone inclusions. 

The octahedral form of the iron ore would sustain the view that it 
was all oi'iginally nuignetite. The difliculty lies in proving the crystals 
to be primary, and not secondary forms, especially as they arc largely 
associated with secondary quartz, and also are abundant in the little 
fissures (minute veins) traversing the jasper. Our microscopic examina- 


VOL. VII. —KG. 1. 

* Gcol. of Wise, III. 615. 




tion of rocks of various ages and cliaractcrs goes to filiow iliat all rocks, 
especially the older, have been subject to more or less alteration. This 
alteration is accompanied by recrystallization, which often obliterates the 
original characters. This change appears to be produced through the 
medium of the percolating watery, and consists rather in a chemical 
rearrangement of the constituents of the rock amongst themselves, 
than in the deposition of any material brought in from extraneous 
sources. The jasper and iron ores, as well as all other rocks examined 
microscopically from this district, have suffered this alteration to a 
greater or less extent ; therefore it is perhaps impossil)lc at present to 
be sure of the original state of the iron, or how many changes have 
taken place. 

Without objecting in any degree to the idea that the ore was origi- 
nally magnetic, certain facts indicate that the present magnetic state 
of the iron is in some places due to secondary causes; i.e. the heat of 
intrusive rocks erupted since the iron ore and jasper w^cre in place. 
While in general the Republic Mountain ore is hematite, exceptions 
exist. On the northerly side of the hill a " diorite " dike was seen (01, 
92). It is found that the ore was so affected by the heat of this intru- 
sive mass that it is magnetic adjacent to it (90), while a short distance 
away it is the normal hematite. IS^umcrous other localities were exam- 
ined about the hill where these secondary intrusions occurred, with the 
same rosidt ; the iron ore was magnetic adjacent to the dikes, but not 
magnetic a short distance away. As a general rule, the magnetite or 
the hematite i)seudomorphs after it (n^iartite) are found near the ''(piartz- 
ite" of Brooks in this mine. Those who examine the njap of Re])ublic 
Mountain, prepared by him,* will observe on the northern side of his 
'*quartzite," a queer tongue of it projecting into the hematite. An ex- 
amination of this tongue at different places shows the following facts. 
It contains numero\is rounded and irregular fragments of the iron ore 
in it; these fragments occur on both edges (93, 94, 90), while the cen- 
tre of the mass is free from them (95). At this point it varies from a few 
inches to two feet in width, and it is seen to break across the lamina- 
tion, although nearly coinciding with it. At another part, shown near 
tlie same pit, No. 8, this rock and its contact with the "jasper" and 
ore were well marked. The "qnart^ito" (115, 118) is firmly welded to 
the ore, and breaks across the laminre, cutting them, and sending 
tongues into^thc mixed jasper and ore (110, 117, 110). The junc- 
tion is an eruptive (intrusive) one, and not that belonging to the con- 

* Atlas, Gool. of Mioli., 18C9~73, Tlato VI. 



tact of one sedimciitaiy rock with anotlier. The ore at the junction is 
magnetic. The question whether thia is an intrusive or sedimentary 
rock has another side than the simple scientific one. It makes a great 
difference in the mine whether this is a simple overlying metamorphosed 
sandstone, as Mr. Brooks places it, or a later intrusion cutting the ore 
below. This latter case opens up numerous questions that the practi- 
cal man can only disregard to his cost, sooner or later, but which have 
nothing to do with the present discussion. 

As this rock seems to belong to the granites, it will be described 
under them (p. 54). Should future research show that all of the 
'' quartzite" of Republic is the same as the tongue is, it would have a 
bearing on the proximity of the magnetite and martite to it. 

In like manner, passing to other mines where secondary intrusions arc 
more abundant, the magnetite becomes a more prominent feature. It 
seems, so far as we have seen, that the magnetite and martite are 
directly proportioned to the amount and proximity of eruptive rocks, 
cxtravasated since the ore was in sitit. 

East of the Old Washington mine, Humboldt, the actinolite schist 
(310) and jasper with its ore (magnetite) were seen within one hun- 
dred feet of one another, but dipping in opposite directions ; three hun- 
dred feet farther west they both dip in the same direction, while a few 
rods away the magnetite (311) with the jasper is seen breaking irregu- 
larly through the schist (312), and sending tongues into it. 

The intrusive nature of the ore was well marked here, but it was very 
difficult to procure any hand specimens showing it (313, 314, 315, 31G). 
An attempt had been made to mine the ore at this locality. Three rods 
to the cast the ore and jasper were seen intruding in long tongues and 
sheets between the planes of the schist, as well as breaking across the 
lamination (317, 318). The same structure is very well marked in the 
rocks that form the blutts between the Old Washington and Edwards 
mines. The ore with quartz (325) sends long tongues up between the 
lamina} of the actinolite schist (32G). Although in part these coincide 
with the bedding, yet in many places they break obliqtiely across it, 
showing their intrusive character in an unmistakable manner. 

It would seem that this intrusion between the planes (intrusive 
sheets) in this locality probably took place whep the schist was in a 
somewhat unconsolidated condition, the intruded rock serving as an effi- 
cient agent of metamorphism. The effect produced by the ore and its 
relations to the schist arc not such as we should expect, or are accus- 
tomed to sec, when a rock is intruded through one indurated as the schist 





is now. The ore at tlie New Washington mine is magnetite, and it was 
seen in distinct well-marked dikes, as unmistakable as any dike, break- 


ing obliquely up through and across the argillaceous schist, No. 340 
showing the contact of the two. These dikes were sometimes narrow, 
being only about one foot wide, with well-marked junctions with the 
schist on both sides. The ore is more strongly magnetic and afTeeted in 
its character adjacent to the dikes that later cut through it than in 
other portions of its mass (p. 43). The dikes of magnetite, with the 
other dikes, have greatly affected the schist through which they pass, 
forming an ottrelite schist (p. 45). At the Champion mine the ore 
is both magnetite (35G) and hematite (355), and both are frequently 
found in a single hand specimen (357, 358, 359). At the Keystone 
mine, east of the Champion, a dike of magnetite about six inches in 
width was observed. 

The Basic intrusive Rocks, Schists, and Pelsito. 

At Marquette, south of, but near, the lighthouse, a dike (3) of about 
seventeen feet in width cuts across the schist (1, 2, 5,), the latter dip- 
ping north seventy degrees. The contact of the dike with the schist 
is a well-marked intrusive one, the schist being indurated at the point 
of coi>tact (4). (Fig. IG.) .Microscopically, the rock of this dike (3) is 
composed of phigioclaye, some orthoclase, quartz, hornblende, biotite, 
viridite, magnetite, l^eraatite, and some probable pscudomorphs after 
olivine. The feldspar contains nvmierous microlites and inclusions, and 
it appears'to be the only original constituent of the rock left in a deter- 
minable condition, except the magnetite. The schist (2) is composed 
of a fine-grained groundmass of aggregately polarizing quartz, liolding 
greenish ragged hornblende crystals and grains of magnetite. 

Many dikes occur in this vicinity, and their intrusive character has 
been noticed by Credner, Eominger, and .Tulien. Some dikes (8) were 
seen running north and south, cutting the east and west ones. The 
relation of one of the latter to the adjacent schists is shown in Figiu'e 
14. In the quarries near the light-house numerous dikes were seen. 
Their lines of junction with the schists (47) could readily be made 
out, and hand specimens obtained showing it (45, 4G, and 48). (Fig. 
15.) Four of these dikes were counted within a distance of two hun- 
dred and thirty-two feet, one of which was sixty-six feet in width (49). 
The locality m the place from which the stone for the Marquette 
breakwater was obtained. These dikes, like the majority running east 
and west, nearly, but not quite, coincide with the bedding (45, 4G, 47, 




48, 49). A specimen of one of these (45), taken near the edge of the 
dike, is composed of plagioclase, orthoclase, magnetite, titaniferous 
iron, hornblende, viridite, quartz, epidotc, and augito. The augite is 
generally nearly altered to hornblende and viridite, only a little of 
the distinguishable augite remaining in the centre of the crystals. 
The other constituents, except part of the feldspar and the iron, boar 
the characters of alteration products. A section adjacent to the 
junction with the schist shows much higlicr alteration. The augite 
has disappeared, the iron has been nearly all altered to " Icucoxene," 
and secondary orthoclase is abundant. The schist from the same speci- 
men (45) is coniposod of quartz, argillaceous material, chlorite, horn- 
blende, magnetite, ^'leucoxcne,'' and a little augite. It would seem that 
this has been formed from detrital material of the same nature as the 
dikes (basaltic). The close resemblance of the '' diorite " and schist in 
mineralogical characters, but not in structure, is shown in another sec- 
tion containing the junction of the two rocks (48). No. 49, taken from 
the centre of the dike, sixty-six feet wide, running parallel with and 
belonging to the same system as the others, is composed of plagioclasc, 
augite, magnetite, olivine, and some viridite. Long microlites of apa- 
tite traverse the mass in various places. The feldspar contains numer- 
ous inclusions of the original base, more or less altered, of the same 
general structure, relations, and arrangement as is commonly seen in 
the feldspars of modern basalts. The portions of the base originally 
left in the crystallization of the molten magma in the interstices between 
the crystals has been changed to a grayish or brownish fibrous sub- 
stance, also to viridite. The augite is comparatively fresh, and cut by 
the feldspar crystals. The structvu-e of the rock is that belonging to 
the more coarsely crystalline basalts. The altered base is probably the 
''inserted substance" of Drs. Zirkel nnd Wichmann.* It would seem 
that some of the above rocks arc like the " diorite " of Dr. Wichmaun 
from this locality (/. c, p. 629). Wc feel that the lithologist who was 
unacquainted with the field relations of the preceding specimens would 
declare it impossible that they covild be from the same series, apparently 
identical in age, and originally so in composition. South of Marquette 
the schists (11) are more argillaceous, forming true argillites, although 
chloritic in places. Numerous dikes were seen here, but the rock is 
more altered, and perhaps was extravasatcd earlier than most of the 
dikes on Light-house point (9, 10, 12). No. 12 is composed of f\^ld- 
. spar, quartz, viridite, opacite, and pseudomorphous remains of liorn- 

* GeoL of Wise, III. 62i. 



blende fragments. But little of tlie(> feldspar shows the twinning of 
plagioclasc. The structure of the rock renders it probable that it was 
originally an andeslte. On Light-house point, lying just north of the 
dike (No. 3, page 3G) first described, and older than it, is an intrusive 
felsite (quartz porphyry). It is to be here noted that Mr. T. B. Brooks 
states : '* It may be confidently asserted that no porphyry occurs in the 
Marquette .... Huronian";* also that this locality has been studied 
by Messrs. Julien, Credner, Rominger, and others, without finding this 

This felbite is eruptive generally along the lamination planes of the 
schist, but at certain points breaks through and across those planes. 
Figure IG gives a good idea of its relations to the schist and diabase, 
for such we regard the rock of the dike to be. A short distance to the 
north, on the opposite side of this immediate spit of land, its eruptive 
character is better marked than in the first locality. 

The felsito (6) on its weathered surface is colored pinkish and green- 
ish white, showing fluidal structure, and holding crystals of quartz and 
pinkish feldspar. On the fresh fracture the groundmass is felsitic, of 
a greenish-gray color, and holds the same crystals. Pyrite is seen in 
the fissures. The groundmass is now altered to an aggregate polariz- 
ing mass, principally of quartz and mica. The fluidal structure is seen 
in the thin section, and greenish and brownish mica is largely segregated 
along the fluidal lines. The feldspar is entirely decomposed, having 
about the same composition and structure as the groundmass, but hold- 
ing more argillaceous material and less quartz. Chlorite and magnetite 
wore observed. The original quartz grains are filled with fluid and va- 
por cavities, and also contain some stone cavities and microlites. North- 
west of the light-house a more quartzosc felsite (7) was found on the 
side of a blufl" overhanging a little ravine. This felsite is very much 
jointed, breaking into small rhomboidal blocks, and cuts through the 
schists nearly, but not quite, coincident witli their lamination. It is 
a grayish-white rock containing crystals of feldspar, quartz, and pyrite. 
Microscopically, the groundmass is now altered to a fine granular ag- 
gregate, as in the preceding, holding quartz, muscovite, greenish mica, 
and pyrite. The feldspar is altered the same as the groundmass, and 
contains similar minerals. The original quartz grains contain micro- 
lites, stone inclusions, fluid cavities, etc. Wo regard these felsitcs, 
from their structure, not as the equivalents or precursors of the Ter- 
tiary rhyoliteSj Ijut as identical with them, the present diflcrence be- 

* GeoL of Wise, III. GGO. 


■ * 



twccn them being duo to secondaiy alteration, and perhaps their some- 
what greater depth at the time of eonsolidation than tlie part of modern 

dikes reached by us had. 

On Picnic Point, north of Marquette, a coarsely crystalhne diorito 
(50, 51, and 52) occurs, forming the main portion of the point. 'J'his 
rock contains pebbles and fragments (53, 54) in some places. Some of 
the fragments of schist are large, and one long baud of it was seen. 
This schist is much indurated, especially near its contact with the dio- 
rite (58, 59), and forms an irregular junction with it (57). Picnic 
Islands, just off the point, are composed, in the main, of the samo 

rock (00). 

On the North Island, a diabase dike (01), about twenty-eight feet 
wide, cuts the *' diorite," running S. 80"" E. Another dike was seen 
running the same way, on the Middle Island. The "diorite" is some- 
what brecciated. On Picnic Point a horublcudic granite (55) cuts up 
through the diabase, and includes numerous fragments of it (5Q). The 
general structure and relations of the granite to the " diorite," as well 
as the rounding off of the '' diorito " fragments, are shown in Fig\ire 17. 
The order is, then, 1st, the schists ; 2d, the " diorite" ; 3d, the granite 

— the question of the priority of either not having been 

and diabase, — 


The '' diorite " (50) is a grayish-black rock composed of hornblendo 

crystals, with reddish feldspar, epidote, and pyrite. Microscopically, it 
contains the same minerals with magnetite and apatite, as well as chlo- 
rite, quartz, viridito, and other alteration products. The feldspars aro 
greatly altered, give aggregate polarization, and are fdlcd with altera- 
tion pi'oducts. 

Tho most coarsely crystalline specimen (52) is a grayish-green rock, 
composed mostly of short, thick hornblende crystals, showing well- 
marked cleavage. With tho hornblende a small amount of feldspar 
occurs. Under tho microscope, besides these, augite, chlorite, quartz, 
titanito, hematite, actiuolite, and magnetite were seen. The horn- 
blende and chlorite appear to be products of alteration from the augite, 
and the hematite from the magnetite. Some of the feldspar can be 
recognized as plagioclase, and it wovdd scorn that tho rock was origi- 
nally composed of feldspar, augite, and magnetite, while the other con- 
stituents aro alteration products. The quartz contains fluid and vapor 

w d * 


The diabase dike rock (01) is a dark gray crystalline one, holding 
ledge-formed feldspars and weathering brown. In tho thin section it is 







seen to be composed of plagioclase, a little orthoclasc, augite, olivine, 
magnetite, hematite, viridite, ^nd apatite. The feldspar encloses bits 
of the original base, part of which is now devitrified, bnt part remains as 
an unchanged globnlitic base. This affords additional proof that the 
diabases are simply old crystalline basalts. Tlio augitc is quite clear 
and unaltered except in some places. The olivine is considerably 
changed, yet the centre frequently shows the unchanged mineral. 
These olivines, like those in modern basalts, are in fragments, grains, 
and rounded and penetrated crystals, showing in this way their prior 
origin to the crystallization of the rock in situ. 

In the sketch of the literature given before, it is seen that Messrs. 
Kivot, Kimball, Hunt, Winchell, Credner, Brooks, and Wright regard the 
so-called "diorites" as sedimentary rocks, metamorphosed in situ, and in 
general teach that they gradually pass into the schists on cither side; 
i. e. they form one and the same inseparable series of sedimentary 
deposits. This passage, by insensible gradations, it is said, was estab- 
lished by the field observations of all except Dr. T. Stcrry Hunt, who, it 
seems, based his conclusions upon lithological evidence ; for we fail to 
find the slightest evidence in his writings that he had any personal 
acquaintance with the district. On the other hand, Messrs. Foster and 
Whitney taught that these rocks were intrusive, basing their conclusions 
upon their observations in the field. 

Special pains were taken by us in the field to see which of the two 
views were correct. Where the conditions were such in the field that 
any evidence could be obtained bearing on cither side, that evidence was 
always of the positive kind, and sustained Messrs. Foster and Whitney. 
The evidence of the six observers quoted on the opposite side was of the 
negative kind ; i. e. they could not or did not see any distinct junc- 
tion between the two rocks ; tlierefore it was assumed that none existed. 
Where the contacts were covered, or broken and obliterated by frost 
and atmospheric agencies, the proof on cither side is nil ; but when 
such is not the case, and we have on one side '' dioritc " and on the other 
schist, the question is. Do they or do they not pass into each other 1 
Both rocks are of a greenish hue generally, and to the eye untrained 
to observe the minutest changes and differences in rocks, they look 
alike. It is therefore to be expected that the •majority, at least, of ob- 
tiervcrs will walk directly over the junction between two rocks, especially 
if they believe in the prevailing theories, and declare tliat they pass 
directly into each other by insensible gradations. The only tiling such 
negative evidence gives in this case is the proof that either the observer 




was aiiskilled, or else his work was not douc with sufficient care, per- 

haps both. The line of contact is, Mlien found, a distinct separation 
between the two rocks ; on one side of which is to be seen schist, on the 
other " diorite." They no more pass into each other than do oil and 
water in the same vessel, although it might not be impossible that some 
would not be able to say where one ended and the other began. The 
contact of the two rocks is so well marked that hand specimens (171, 
172) can bo obtained showing it; therefore our proof that they do not 
pass into each other, but are entirely distinct formations, can be exam- 
ined not only in the field, but also in the cabinet, and if need be under 
the microscope. 

Such a contact between the schist and " diorite *' can bo seen a short 
distance east of Ishpeming, where the carriage-road, near the railroad 
leading to Negaunee, bends around a low "diorite " knob. This junc- 
tion is represented in plan (Fig. 18) l)y a sketch made on the spot, 
and shown by specimens 171, 172. The "diorite " at this point appears 
to have passed oblicpiely up through and over the schist. The relation 
that the two have, the kind and manner of contact, are those beloiiirino- 
to an eruptive rock breaking through and partially over another. It is 
almost needless to say that the "diorite "is the eruptive rock here. 
Many of the " diorite '' hills, if not all, arc composed of dikes of the 
"diorite," with schist and argillite lying between. The lamination of 
these interlying masses is of course generally perpendicular to the pres- 
sure, i. e. parallel with the dikes. This can be well seen in the hills 
south of Teal Lake, Negauuce, as well as just northeast of the Cleve- 
land mine, IshpGming. At the latter place the "diorite " is seen to 
break obliquely through the schist, and the line of junction can be easily 
seen. (Fig. 19.) So far as can be told, the "diorite" comes out ob- 
liquely over the schists connected with a narrower neck below, as shown 
in ideal section. (Fig. 20.) This would indicate, we think, that this 
is somewhat near the old surface of eruption. This hill was seen to be 
made up of several "diorite" dikes, with schist held between them. 
The contact of two of them with the schist is shown in Figures 21, 22. 

At Negauuce, on a little elevation between Main' Street and the 
Marquette, Houghton, and Ontonagon Railroad, the " diorite " is seen 
to break through the schist, and to send small veins into it On the 
"diorite " ridge south of Teal Lake, the "diorite "is seen (243+, 282, 
283) to have cut through and enclosed between it some schists and 
argillltes. This rock is very columnar, and has the general character 
of an eruptive mass. Its junction with the schists is well marked, and 

I 1^ 
I I- 




was observed in various places. One specimen is seen to be composed 
of augite, hornblende, feldspar, viridite, titaniferous iron, and epidote 
(243+). The augite is much altered, changed to viridite and hornblende. 
Another section (283) shows no augite, this mineral being entirely re- 
placed by the secondary hornblende. The feldspar is so greatly changed 
that only part of it shows its tricliuic character. Of a similar character 
to No. 283 are Nos. 238+ and 239+, from the "diorite" south of Lake 
Superior mine, neither showing any augite, although the hornblende is 
doubtless secondary, as in the others. No. 239+ is more coarsely crys- 
talline and granitoid in its structure. 

The "diorite" (180) lying between the Lake Angeline and Salisbury 
mines is seen in the thin section to be composed of plagioclase, horn- 
blende, biotite, epidote, viridite, and titanifei'Oiis iron with its alteration 
product. Of these only the feldspar and titaniferous iron arc aj)par- 

ently original constituents. 

The diabase (175) forming the southeast side of the Salisbury mine 

is a dark gray crystalline rock, holding ledge and tabular formed crystals 
of feldspar, and weathering to a rusty brown. It makes a most beauti- 
ful section under the microscope when studied in polarized light. It is 
composed of plagioclase, orthoclase, augite, magnetite, olivine, viridite, 
and hematite. The plagioclase cuts through the augite, leaving it in 

cuneiform and irregular masses. 

The olivine is in rounded and irregu- 

lar grains of prior origin to the crystallization of the rock, and is held 
both in tlie feldspar and in the augite. It holds a similar relation here 
to the feldspar that it does to the cnstatitc in the Presque Isle pcridotito. 
While the central portions of the olivine arc sometimes clear and un- 
changed, the grains are generally altered to a greenish or brownish ser- 
pentine. A little fissure traverses the section, cutting and connecting a 
number of the olivines. This fissure can be readily traced under the 
microscope on account of its having been filled throughout its extent with 
the greenish serpentinous material derived from the olivine. The feld- 
spar is in some cases nearly filled with stone inclusions, arranged parallel 
to the crystalline faces. These inclusions are evidently inclusions of a 
devitrified base. This dike is said to ascend by steps, not in a straight 


Near Deer Lake, northw^est of Tshpeming, a *' diorite " dike running 
N. 45° W. (231) was seen cutting a breccia and conglomerate (229, 
230). This ''diorite" is so altered that it resembles a chlorite schist, 
and in the thin section is seen to be composed of chlorite, quartz, and 
mica. It holds some ferruginous masses resembling the product of 




the decomposition of titaiiifcrous iron, as well as one or two that proba- 
bly resulted from the decomposition of oHvino or brown hornblende. 
The quartz contains fluid inclusions. The groundmass is now composed 
entirely of scales, plates, grains, and microlites belonging apparently to 
chlorite, mica, and quartz, and with the exception of the ferruginous 
decomposition product no trace of the original structure and constitu- 
ents remain. We regard the rock simply as a more highly metamor- 
phosed condition of the "dioritcs" of the region; but were it not for 
its field relations we should not bo able to tell its history from micro- 
scopic examination. In such a case as this, with our present knowl- 
edge, the microscope fails to give us any idea of its origin, whether 
eruptive or sedimentary. Probably every lithologist, in examining this 

I 1 

section, would pronounce the rock to be sedimentary, yet we know it 
to be eruptive, and probably in its original state a basalt. This well 
illustrates the danger of deciding npon the origin of such highly altered 
rocks by microscopic analysis alone, and calls attention to the necessity 
of carefully ascertaining their relations in the field. 

One mile northwest of Deer Lake, west of the road, a high hill w^as seen 
composed principally of "diorite" (232) running about north and south. 
The contact of this " diorite " with the country rock is well marked on 
both sides. On the west side it cuts a conglomerate, and on the east 
a fincr-gralncd fragmcntal rock (233). The contact is an irregular 
eruptive one, and the country rock is indurated near it. At the south 
pit of the Jackson mine, from which *'soft hematite" is taken, a 
diabase dike forty feet wide was observed running N. 30° W., and cut- 
ting the ore. It was said that in mining its conrse had been found to 
be variable. This diabase is a grayish brown, coarsely crystalline rock 
composed of plagioclase, orthoclase, augite, brownish decomposed olivine, 
magnetite, and ferrite (278). The plagioclase is but very little decom- 
posed, and is beautifully striated. The diabase (280) near its walls was 
very much decomposed, and its olivine, augite, and magnetite form a 
dark brown decomposed mass cut through by the feldspar crystals, which 
are kaolinized, forming feebly polarizing masses. Were it not known 
that it is part of the diabase, it could only be recognized as such from 
the position and arrangement of its kaolin pseudomorphs relative to 
the remaining portion of the section. 

In the Washington mine several dikes of " diorite " and melaphyr cut 
the ore, which is strongly magnetic in contact (327, 328) with them. 
The melaphyr (329, 342) encloses a horse of jasper and cuts the "dio- 
rite." It (329) is composed of j^lagioclase, a little orthoclase, augite, 







magnetite, and viridite. • The strnctnre is that belonging to basalts, and 
the rock is comparatively little altered considering its age. The feld- 
spars contain inclusions that appear to have been portions of the origi- 
nal base, but whtch, as well as the base adjacent, has been altered to 
a grayish-white globulitic and fibrous material. This shows largely 
the structure of the original globulitic base, but wants the black color. 
The fibrous alteration product of the base has been confounded with 
the true original micro-felsitic base of the andcsites by lithologists 
generally ; as is the inevitable result of studying tlie constituents of 
rocks without regard to the origin of these constituents. A very little 
of the original globulitic base was ibuiid unchanged in some of the 
feldspars. IS^umerous microlites extend through the groundmass that 
belong apparently to apatite. This is probably from the same dike that 
No. 1110 of Mr. Brooks's collection, described by Dr. Wichmann, was 
obtained.* The "long, small rod-like crystals" in which the plagioclase 
is said to occur is the usual ledge form which belongs to basaltic plagio- 
clase. The " inserted substance, which has not been individualized," is 
doubtless the altered globulitic base. No biotite or hematite were seen 
in No. 320, which was selected with direct reference to procuring as 
unaltered a specimen as possible, as well as one removed from the influ- 
ence of the ore and jasper (342) through which the mclaphyr cuts. A 
section showing the jimction of the two rocks (342) was made. The 
mclaphyr here becomes a dense black opaque mass, containing a few ledge- 
formed plagioclase crystals and some decomposed (viriditic) augite. Thia 
part is probably an altered tachylitic glass, such as occurrs in similar 
positions in basalts. The junction with the jasper is w^ell marked, and 
more regular than one would expect to find it. The globulitic structure 
shows well in the melaphyr at this immediate line of contact. The 
*' jasper" is composed here of quartz and magnetite. The quartz is in 
part fine granular, and filled with magnetic dust ; while the remainder 
is coarsely granular, having the same structure as the granite (greiscn) 
southwest of Republic Mountain (No. 128, p. 53). These quartz grains 
were formed by the fissuring of a quartz mass, not built up of detrital 
quartz grains, as is the case with a true quartzite according to the defi- 
nition employed by us. The quartz contained numerous fluid and stone 
inclusions, as well as microlites, magnetite, and lenticular scales of proba- 
ble muscovite. 

The "diorifco" (334, 335) cutting the magnetite yielded specimens 
showing a well-defined contact (337, 338, 339). No, 335 is a grccnish- 

* Geo!.' of Wise, in. 625. 



gray rock composed of hornblende, holding patches of quartz, which con- 

tains crystals of tourmaline. The rock holds an abundance of magnetite, 
in part at least torn from the ore through which it passed. The quartz 
contains Huid and other indubious. The schist at this locality is an 
argillaceous one (340) resembling that found at Republic Mountain, 
Ishpeming, and Negaunee ; but it has been so affected in places by the 
combined action of the magnetite and other dikes that it has become an 
ottrelite schist (33G). This rock has a dark gray groundmass, holding 
crystals of ottrelite and minute ones of tourmaline. In the thin section 
the groundmass is of a clear grayish-white color, and holds ottrelite, 
tourmaline, and magnetite. This groundmass is composed of a clear talc- 
hke mineral in flakes and scaler, apparently orthorhombic. In it occur 
magnetite grains and irregidar masses of this mineral, as well as greenish 
micaceous scales. The ottrelite in the section is of a green color, shows 
dichroism, varying from a light to dark green, and contains scales of the 
talc-like mineral, magnetite, etc. In polarized light it shows a banding 
generally of lighter and darker shades of the same color. Its edges are 
broken, step-like, and irregular ; and it shows cleavage parallel to the 
basal and lateral planes. In microscopic characters it and the masonite 
of Warwick, 11. L, are closely alike. The tourmaline is in elongated 
crystals containing grains of magnetite. All the minerals in this rock 
are of later origin than the magnetite. 

South of the Champion mine dikes of diabase (34G) and "diorite" 
(345) opcur in the granite and gneiss. A " diorite " that was undis- 
tinguishable from that in the gneiss (345) was found at the east end 
of the Champion mine, in the '* Huronian." This *' diorite '* contains 
patches of quartz, which hold crystals of tourmaline in radiated groups. 
The '^diorite" (345), running north and south in the " Laurentian," cuts 
both the granite and the gneiss, and is composed of hornblende, biotite, 
quartz, and magnetite. Traces of some of the larger and more porphy- 
ritic feldspar crystals remain in a kaolinized mass, containing flakes of 
biotite and grains of quartz. Were the origin of this rock unknown, it 
would pass for a sedimentary hornblende schist, so. far aa the section in- 
forms us of its nature. The diabase (346) is comparatively fresh, and 
is undistinguishable from the diabases seen in the "Huronian." It is 
composed of augite, plagioclase, a little orthoclase and quartz, mag- 
petite, viridito, and some decomposed olivine. 

Another dike (343), cutting the gneiss at this locality, is seen to bo 
composed of hornblende, quartz, feldspar, and magnetite. 

On the northerly side of Eepublic Mountain a garnetifcroua "diorite " 

i :rl 



(91, 92) was observed cutting across the iron-bearing rocks, bending and 
breaking them at the junction between the two. The " diorite " holds 
fragments of the iron-bearing rocks in it, and cuts very irreguUirly 
through the schists. Its intrusive character is distinctly marked hy the 
relation which it holds to the country rock. It renders the rock adja- 
cent to it magnetic for a little distance from the junction. A section 
taken from a specimen (92) free from garnets is seen now to be com- 
posed almost, if not entirely, of sccojidary minerals, —a confused aggre- 
gation of greenish hornblende, orthoclase, quartz, and biotite, with 
traces of magnetic iron. The character of the hornblende is the same 
as that seen to occur in those rocks whose hornblende is derived from 

the augite by alteration. 

To the southeast of this locality, not far from the granite, the iron- 
bearing rocks were again found in contact with a similar garnetiferous 
*' dioritic " dike ; the former being much contorted and broken, the iron 
being also magnetic near the contact. A tongue of the " diorite " pene- 
trated the ferruginous rock, and the relations were such that it was 
evident that the contortion was owing to the intrusion of the "dio- 
rite." The "diorite" (121) marked on Mr. Brooks's map of Ecpublic 
Mountain, lying between the quartzite and Smith's Bay, is seen under 
the microscope to be very much altered, and composed of hornblende, 
biotite, plagioclase, orthoclase, quartz, and magnetite, with a little hema- 
tite. Of these minerals, it would seem from their structure and rela- 
tions, that only the magnetite and part of the feldspar were original 


The basic intrusive rocks mentioned in the preceding pages have, in 
general, been regarded as diorite, Mr. A. A. Julien especially doubting 
the presence of any diabase in the region.* They would pass, according 
to the ordinary definitions, macroscopically and microscopically, for dio- 
rite, quartz di(frite, diabase, chlorite schist, hornblende schist, etc., yet 
we regard them all simply as more or less altered forms, according to 
age and conditions, of rocks that were originally the same in origin. 
Structure, composition, and name, — basalt. Of course, the supposed 
altered andesite (p. 38) would be an exception. The reasons for so 
regarding them have been briefly pointed out in this and preceding 
papers.+ Excepting the melaphyr of the New Washington mine, we re- 
gard them all, then, as the alteration form of basalt known as diabase. 

* GeoL of Mich., IL 42, 193. 

t Proc. Boston See. Kat. Hist, XIX. 217-237, 309 
Zoology, Cambridge, V. 275-287. 

310 ; Bull. Mus. Comp. 



At Republic Mountain, on the southwest side, a garnetiferous "dioritc " 
was seen in direct contact with the jasper, whicli was much twisted and 
contorted. The ore associated with the jasper was magnetic. The 
" diorito " was found to be intrusive here and elsewhere about HepubHc 
Mountain, breaking through and uphfting the overlying rock, whoso 
hiniina3 it is seen to cut obliquely. It also sends stringers and dikes 
into the schist and jasper. As the " diorite" passed approximately alon^>- 
the lamination of the schists, and is foliated parallel to its walls, it is easy 
to see how those who believed that, if a rock was '*stri2:)ed," it was ^:>nVMa 
facie evidence that it was a sedimentary one, should overlook the eruptive 
characters. Most of the " diorites " here contain garnets, this mineral 
being found principally along the edges of the intrusion, while the cen- 
tre was nearly, if not entirely, free from it. The schist, in like manner, 
near the *' diorite," also frequently contains garnets, both rocks aj^pcariug 
to have mutually reacted upon each other. Under the microscope, one 
of these ** diorites " (124) is seen to be composed of actinolite, garnet, 
quartz, and biotite. The arrangement, forUi, and relations of these indi- 
cate that none of them are original constituents of the rock, but all are 
the products of altei^ation. 

A dike of dark micaceous "diorito" (123), some ten inches in width, 
was seen near this place, which contained garnet crystals varying from 
one half an inch to two inches in diameter, averagiLg nbout three 
fourths of an inch. These garnets, like the others observed, are dode- 
cahedrons. Microscopically it is seen to be composed of biotite, quartz, 
feldspar, and magnetite (?) with the enclosed garnet crystals. The 
black grains have the microscopic charactei-s of magnetite, although tlio 
powder is not magnetic. The biotite is the predominating mineral, and 
all tlic present constituents, except, perhaps, the supposed magnetite, 
appear to be secondary products. The garnet is filled with the magnet- 
ite (]). These black inclusions, so far as we are aware, have been taken 
for magnetite,* except some observed by Professor Pnmpelly.f In po- 
larized light the garnet is seen to contain abundantly the same grains ot 
quartz and feldspar that the groundmass does ; it also holds some biotite. 
Tiie "magnetic siliceous schist" of Mr. Brooks (12G)niear the granite 
(128, 129, 130) southwest of Republic Mountain (p. 53), is seen micro- 
scopically to be composed of actinolite, hornblende, magnetite, and 
garnet. The two first form the major portion ,of the section. The 
garnet is filled with needles of actinolite. Southeast of Republic Moun- 
tain, the same rock (No. 100, p. 53) contain-s longer and better formed 

* Geology of AAlsc, III. COS. 

t Am. Jour. Sci., (3,) X. 20. 



crystals of actinolite. Besides actinolite, the chief constituent, it also 
contains magnetite, garnet, and a little hematite. The garnet contains 
inclusions of actinolite. The garnetiferous rock (97) adjacent to the 
granite (p. 52) is composed of actinolite, quartz, garnet, and a little 

secondary hematite. 

Southeast of the Old Washington mine a dike was seen breaking 
irregularly through the schists. Near the centre of the dike, the rock 
(305)' resembles a chlorite schist, but is composed of actinolite, mag- 
netite, quartz, biotite, and muscovite, none of which appear to be 
original constituents, except perhaps the magnetite. A specimen near 
the exterior (306) was more massive, but contained the same min- 
erals. Part of the iron showed the decomposition of titanifcrous iron. 
No. 307, from the edge of the dike, closely resembles a ehloritc schist, 
and contains garnets and well-formed crystals of tourmaline. No. 308 
comes from the edge of the dike, and is so filled with garnets as to 
resemble eklogite. Neither of the four specimens would macroscopi- 
cally be. taken as belonging to the same rock if their relation was not 
known. This is probably the rock described by Dr. Wichmann as eklo- 
gite.* The schist at the point of contact is much indurated and quartz- 
ose, and the garnets make an irregular columnar mass adjacent to it 
(309). They are so crowded and drawn out at right angles to the schist 
that their structure very closely simulates the prismatic structm-c of a 
basaltic dike. Such structure and arrangement of minerals, in a ring, 
parallel to the surfjxce of the enclosed fragment, is frequently seen about 
quartz grains and other foreign materials included in the volcanic rocks 
of the Cordilleras. Several other dikes of the same rock were seen 
near this. All were very much contorted, breaking very irregularly 
through the schist, and showing intrusive characters. 

The actinolite schist south of Humboldt was seen to pass into a quartz- 
ose rock made up principally of alternate layers of quartz and actinolite 
(319, 320). This shows very conclusively the sedimentary origin of the 
schist here. The banded magnetic schist of Mr. Brooks southeast ot 
the Champion mine (No. 348, p. 57) is seen microscopically to be com- 
posed of a thick mat of actinolite holding garnet, quartz, and magnetite. 
The magnetite is surrounded in many cases by thin films of hematite, 
derived from the magnetite, and extending between the actinolite crys- 
tals. The same hematite films extend around the garnet and penetrate 
along its fissures, giving it a deep red color, but leaving the centre often 
clear. Only a little quartz was observed. 

* No. 1091, Gcol. of Wise, IIL 649. 



These garnet-bearing, actinolite, intrusive rocks we cannot at present 
definitely place in that position which sccnss to ns proper. In order to 
do that, it is necessary to have part at least of the original structure or 
constituents preserved; this we did not iind. So far as we can judge, 
tliey are probably altered basalts or andcsites, most probably the former ; 
this conclusion is, however, liable to be overthrown by new evidence 
at any time. The reason for this decision is in the main their rehx- 
tion in minerals, position, antl structure to the other highly altered 
*' dioritcs," especially at Republic Mountain. The actinolite schists 
wore in all probability formed from detritus of the same composition 
as the dikes, and therefore under like conditions are mineralogically 
about the same. 

In the Lake Superior mine, a banded greenish quartz rock resembling 
prase was observed. In the thin section it is seen to be composed of 
quartz containing magnetite and innumerable little scales of greenish 
mica. The green color is due to the latter. Some fluidal inclusions 
were observed. The quartz shows the granular aggregate polarization 
observed in connection with the devitrification or alteration quartz in 
rhyolites and fclsites. The relation of this rock to the ore and jasper 
was that of an intruding, fracturing, uplifting mass, breaking across the 
lamination but not reaching the surface. Above, and adjacent to it in 
the disturbed jasper and ore ''soft hematite" was found. This rock, wo 
think, would make a very pretty object when polished. 

■ ■■ 

The " Soft Hematites," 

One of the best localities that we have seen to study the formation of 


the *'soft hematite" is at the Salisbury mine, Ishpeming, just south of 
the Lake Angeline mine. A "diorite" hill lies between the two mines, 
wdiich, when erupted, we believe upheaved the jasjior and hematite lyitig 
on both sides of it. ■ At the west end, on the north side of the hill, the 
Lake Angeline mine is situated, and it is still an open question whether 
the ore formation does or does not extend eastward along the flanks of 
the hill. On the southern side, towards the northern end of the hill, 
the Salisbury mine is located. This is a "soft hematite," which is held 
by Mr. Brooks to belong to a different formation, in general, from tlie 
hematite. We regard it as the same formation as the jasper and its 
associated ore, but which has been acted upon by thermal waters. All 
the writers on the "soft hematites" of this district have regarded 
them as formed from the decomposition of ferruginous schists by thermal 

VOL. VII. — NO. 1. 4 



waters, and on this point wc arc in accord. In general they regard them 
as peculiar to certain formations making a bed or set of beds in the 
stratigraphical series below the ore formation proper, while we regard 
them simply as local modifications of the ore formation of the region 
occurring under certain conditions ; i. e. the conditions that led to the 
shattering of the rock and gave the opportunity for the formation of 
thermal springs. On one side of the Salisbury mine is the " diorite/' 
while on the other comes a strong dike of diabase (p. 42). The "dio- 
rite*' runs about east and west, while the strike of the diabase is about 
N. 50° E. The latter is seen to be the younger rock, and the marks of its 
passage through the ** diorite" hill can be seen a long distance off. The 
relation of the two rocks is shown in the plan (Fig. 23), while the supposed 
relation of the "diorite'* to the schist and ore is given in Figure 24. 

The Salisbury mine is located in the acute angle a, formed by 
the two intrusives, at the point where the fracturing, breaking," and 
shattering of the prior or ore formation was greatest, and where hot 
springs would then most likely occur. The general structure of this 
rcirion, the character of the ore and its associated kaolin, all confirm, in 
our mind, this view. As the ore deposit formed under such conditions 
is necessarily limited, it has become a matter of great importance to the 
company working this mine to find a continuation of this ore, or a new 
locality, before the old is completely worked out. The mining captain 
informed me that the State Geologist, Dr. Rominger, in conformity with 
his views and those of Messrs. Brooks, Kimball, and others, that the 
diorite, diabase, jasper, hematite, and limonitc are distinct sedimentary 
formations, advocated the sinking of pits at the points h, c, d, where 
the formation would, by its foldings, again be brought up, and give the 
same ore. The point h is located at the obtuse angle of the junction 
of the diabase and diorite, therefore wc should not expect so much shat- 
tering of the rock, nor so great likelihood of thermal springs. "Soft 
hematite" would be expected to occur to some extent, but with too 
much of the undecomposed jaspery rock to make it profitable mining. 
Such was found to be the case ; therefore the theory of Messrs. Piomin- 
ger. Brooks, and others fliilcd here. If the T.akc Angeline ore formation 
extends cast along the northerly side of the "diorite" hill, the most 
likely place to find a deposit of "soft hematite/' if our views are cor- 
rect, would be at the point A, in the acute angle formed by the dia- 
base with the " diorite," as it breaks through the latter. Unfortu- 
nately this point is not on the property of the Salisbury mine, and it 
slumbers in its primeval mud: 

■"^ x^^^-rrr-jM .U^ --^ . . .n . -r^-r-j- j- n^-^-p^ rr^ t^ ,^n^ n 



The McComber mine, Negaunee, is a mine of "soft hematite"; this, 
in connection with others lying along the same line, is near the "dio- 
rite." Part of these mines, however, lie between two hills of the "dio- 
ritc." Two deposits occnr on the McComber property, separated by a 
dike of the "diorite." The ore here, like that in the Salisbnry mine, 
seems to occnr only where the rocks have been shattered and acted npou 
by water. The jasper has decomposed (244+), yielding a hydrous 
silicate of alumina (Kaolin, Brush) (2454-, 24G+), quartz, hydrous and 
anhydrous oxide of iron, etc. The minerals associated with the ore are 
evidently water deposits, —barite (253), rhodochrosite (249H-, 250+, 
25 1+, 252+), manganite (247+, 248+), etc. Figure 25 shows the fornia- 
tion of the ore under a jasper cap, the water working in by the means 

of fissures on both sides. 

The Pcndill mine, worked for a similar ore, contains much botryoidal 
limonite (254). In one part the ore was worked out upon the top and sides 
of an oven-shaped mass, the ore following the curvature of the oven. 
This is similar to a form observed in the Lake Superior mine, associated 
likewise with limonite. In the Jackson mine "soft hematite" occurs in 
places, and it is seen to be associated with and to pass directly into the 
jasper and " hard ore," showing that they were originally the same. Water- 
deposited quartz (vein-stone) w^as found in places in this "soft ore," and 
a specimen was taken for microscopic examination (27G), for the pur- 
pose of seeing whether it contained fluid cavities or not. It is found to 
be full of inclusions, most of which contain bubbles. These bubbles 
were, in the majority of cases, seen to exhibit motion of greater or less 
rapidity. Some were seen containing double inclusions, and vapor cavi- 
ties were observed. All would indicate that the water by which the 
quartz was deposited was at a higlier temperature than the rock has 
at present. This then would seem to confirm the views of all the 
writers quoted, as well as of ourselves, that these ores are derived- from 
the decomposition of the ferruginous, siliceous rocks. That this is the 
correct view of their origin it would seem Dr. ITunt denies.* 

The various soft ores are partly true hematites and partly limonites, 
mixed with more or less impurities, but of course, in goncral, have none 
of the characters of an ordinary bog-iron ore. 

Our theory, of course, depends upon the relation of the " dioritcs " 
to the jasper and ore, which near Ishpeming and Negaunee is some- 
what uncertain ; yet there is but little doubt that the "diorite " is the 
later. The dip of the jiisper increases as it approaches the "diorite," 

* Geol. of Wiac, III. 660. 







sometimes standing nearly vertical. It was not observed in contact with 
the " diorite," but wc feel that the conatant uptilting of the jasper and 
associated schists when near these intrusive rocks is good evidence that 
the *'diorite" eruption was later than that of the jasper. The nptilting 
of the jasper was well seen on a hill north of the Jackson mine, where 
it was found, standing nearly vertical, within one hundred feet of the 
" diorite." 

Granite, Gneiss, and Quartzite, 

The relation of the granite and its associated foliated rocks to the 
schists of the Iron district is a problem of great geological importance. 
The diverse views have been given on preceding pages, and it is not 
necessary to repeat them here. The first-mentioned rocks have been 
accepted by the Canadian geologists (in part at least), as well as by 
most American ones, as the direct equivalents of the Laurentian 
formation of Canada, while the latter is in the same way accepted 
as the equivalent of the liuronian. Without going into the question 
of the expediency or right of establishing geological ages upon any 
other basis than that of organic remains, it is a fair question of in- 
quiry whether the " Laurentian" of Lake Superior is older or younger 
than the " Huronian.'' Whose observations were the nearest correct, 

those who claim that the granite is intrusive in the schists, or 
those who hold that it unconformably underlies thcml On one side 
we have the statement of direct intrusive contact ; on the otlier, the 
evidence afforded by the fact that the strike and dip of the foliation of 
the two rocks are unlike, the two formations never having been seen 

in contact. 

It is now time to give the facts observed by us. 

North of Kepublic, })y the side of the railroad, a few rods from the 
depot, the grauite (82) (Laurentian of Brooks) shows its intrusive char- 
acter by its containing fragments of schist (83) in it, and by its cutting 
the main body of schist. These schists are micaceous, hornblendic, and 
chh)ritic, with a nearly" north and south t^trike, the foliation of the 
granite coinciding with it. Northwest of the track, near the above- 
mentioned locality, the inclusions in the granite are well marked, the 
foliation of the granite striking S. 20° E. Southeast of Republic Moun- 
tain, separated from the supposed *' Huronian " by a narrow ravine, 
the granite was observed in contact with a garnetiferous actinolite rock, 
beautifully banded and contorted (No. 97, p. 48). While this appears to 
us to be identical with the '41uronian" rocks, a few rods away, resembling 




the actinolitc sclusts of Wichmann (100, p. 47), Mr. Brooks believes* it 
to be " Laurentian," for no reason that we can see except that it is associ- 
ated with the granite. This rock has been tilted and contorted by the 
granite which is found in contact with it. The line of junction and the 
manner of contact show that tlic granite was the later rock and an erup- 
tive one. ThefoHation of the granite is parallel to the plane of contact, 
or at right angles to the pressure. It contains fragments of schist (98), 
while some highly quartzose schists or quartzitcs (99) were seen within a 
few feet of it. These rocks were apparently older than the granites, and 
had been affected by them. On the southwest side of Republic Mountain 
the i^ranitc was seen about one rod from the " Huronian" schists. This 
is probably the locality figured by Mr. Brooks,t but the foliation of both 
appeared to us to be conformable in this way : the schists appeared to 
have been jjartially uptilted by the granite, which seemed to have been 
extravasated oblitpicly out from under them, very much as the perido- 
tite was under the sandstone at Presque Isle. The foliation is parallel 
to the plane of pressure, and at right angles to that pressure. 

The granite near the edge is finc-gniincd, resembling a quartzite 
(128), but a little distance away it is coarser and more granitoid (129). 
Borne upon the face of the granite next to the schists is a plate of rock 
about two inches thick (130). This is welded closely to the granite, 
and has been uplifted and altered by it. lis constituents have been 
drawn out in the direction of the supposed motion of the granite, and re- 
semble in the field the altered garnetiferons " diorite " (123) described on 
page 47. The rock is micaceous, of a dark gray color, and contains elon- 
gated brownish-gray masses resembling altered garnets. Microscopically 
it is seen to be composed of biotitc, muscovite, quartz, and the garnet(?) 
masses. The last arc now composed of a fiuely fibrous aggregately po- 
larizing material holding quartz grains, magnetite, and apparently hex- 
agonal or orthorhombic opaque disks. Their nature is unknown, but 
they most probably belong to the margaropliyllites.t Whether this 
rock was originally the same as No. 123 told, although in 
many respects it closely resembles it. Should it be, the granite there 
is younger than the ''Huronian diorite." 

The granite (129) is seen in the thin section to be composed of quartz 
with some green mica. Not the slightest trace of feldspar was found. 
The quartz is broken up into grains, which exactly fit to one another 
without any cementing material. The granular structure arises not 

* Geol. of Wise, III. OCl. 
t Gool. of Mich., I. 126. 

t Am. Jour. Sci., (3,) X. 20. 



from original water-worn grains, but from the Assuring of an originally 
continuous siliceous mass. The quartz contains fluid cavities, micro- 
litcs, and little flakes of mica. IS'"o. 128, nearer the Huronian, at the 
edge of the granite, is microscopically seen to be in finer quartz grains. 
This rock also contains greenish mica, clusters of actinolite crystals, and 
garnet grains. The quartz graiiis contained the same inclusions as 
those in No. 129. Some magnetite was observed. The actinolite crys- 
tals were often seen to extend through two or more of the adjacent 

quartz grains, not having been broken by the process of Assuring the 

Specimen 130 consists of two parts, — the schist already described, 
and the granite to which it is welded. This granite is here composed 
of quartz, biotite, and grains of garnet. The quartz is in the same fis- 
sured grains as that in Nos. 128 and 129, and contains microlites, minute 
crystals of greenish mica, and fluid cavities. The majority of the fluid 
inclusions lie in the secondary fissures, but part are in the solid quartz. 
The biotite is seen to frequently extend from one quartz grain into an- 
other without having been broken by the fissuring of the quartz. The 
garnet contains actinolite crystals,.. and the same black grains that it 
did in the adjacent schist (130). The biotite and garnet arc evidently 
derived from this schist, and are in fragments. This section, more 
than either No. 128 or 129, shows the effect of the schist in adding 
foreign ingredients to the granite, and also the action of the granite on 
the schist by tearing off and dissolving portions of its material. Such 
phenomena are the usual accompaniments of the mutual reaction of 
two rocks when one is intruded through the other. The three sections 
128, 129, and 130 well illustrate the difl'crences that can be observed in 
the same rock within a distance of a few feet. 

It seems appropriate to describe with the granites las.t given the 
"quartzite " (page 34) of Mr. Brooks at Republic Mountain. The rock 


(95, 115, IIG, 117, 118, 119) is greenish gray, macroscopically containing 
quartz, actinolite, and epidote. Under the microscope it (115, 118) is 
seen to contain quartz,- actinolite, hornblende, greenish mica, epidote, 
magnetite, and hematite. The quartz is in similar grains to that in 
Nos. 128 and 129, and contains numerous microlites arid mica inclu- 
sions, as well as fluid cavities. This rock, it would seem, belongs to the 
granites adjacent to Ilepublic Mountain, and is an offshoot from them. 
In microscopic characters tliey arc closely allied, but we only ofler this 
for what sucii characters are wortii in such questions as these. One thing 
we know. This (" quartzite ") granite is eruptive in its present lAace, 




and if it is part of the same formation tltat the adjacent granites are, 
then the latter arc younger in their present position than the iron ore 

of RepubUe Mountain. 

The preceding rocks (128, 129, 130) naturally fall under the name of 
grelsen, but as they seem shnply to be the modified edge of the '' Lau- 
rentian" granite, we prefer to apply the name granite to them. The 
practice of giving a diftercnt name to every little local modification in 
rocks has been a constant source of confusion in lithology. This prac- 
tice has perhaps never been carried to greater extent than it has been 

in this district.* 

South of Ishpeming, on the line of the Chicago and Northwestern 
Eailroad, a gray gneiss (192, 193) was seen dipping W. 33°, cut by the 
common reddish granite (194), which sends veins through it. Figure 26 
was taken here from the side of a little cliff (195). The gneiss, at the 
points in which it is cut by the granite, is less schistose, and becomes 
more granitoid in its structure. A few rods west, on the north side of 
the railroad track, this granite is seen in contact (197) with and cutting 
aqnartzite that resembles the ordinary ''Huronian" quartzites. The 
granite is here in large masses, but shows its intrusive character when 
in contact with the gneiss, quart/ite, or schists. About one eighth of a 
mile nearer Islipeming the granite (202) was seen in contact (200) with 
and contorting schists (201, 203). This shows its intrusive character on 
both sides of the schist, the contact being well marked in many places. 
On the same elevation a fine-grained granite (204) was seen to be intru- 
sive in a dark green nodular schist, containing large irregular masses 
of feldspar (205). These schists and granites are in the area mapped 

as "Huronian" by Mr. Brooks. 

The granite breaking through the '' diorite'* at Picnic Toint has been 
referred to (page 39). This appears to be the same as the reddish 
granite that occurs at the mouth of Dead River (62, G3). The lamina- 
tion of this latter granite strikes S. 80° E. The reddish granite of the 
entire region appears to be lithologically the same. That breaking 
through the "diorito" at Picnic Point (56) is seen to be, under the 
microscope, a crystalline aggregate of feldspar, quartz, and hornblende, 
with magnetite. The feldspar is in part clear orthoclase, but mostly a 
pinkish decomposed one without definite polarization. This, according 
to the present imperfect method of microscopic analysis, is presumably 
orthoclase, but we believe it may or may not be so. This feldspar is 
now composed of a fibrous deconq)osition product, kaolin C?), with ox- 

'* Sec Gcol. of Midi., Yol. II. 



ide of iron and quartz. Contrary to the views of Dr. Wichmann and 
Prof. Zirkcl, we regard these as the products of decomposition of the 
feldspar and its enclosed foreign materials, and not originally formed 
products. Likewise we find the same alteration products in distinguisli- 
able plagioclase as well as in orthoclasc.* The quartz occurring in the 
feldspar appears to be a secondary product, as also is part of that occur- 
ring independently in the rock. Many minute microlites occur in the 
decomposed portion of the feldspar as a secondary product. The quartz 
contains fluid cavities and microlites. No salt cubes were seen in the 
fluid inclusions. It will be remembered that Air. Charles E. Wright 
pointed out that what he supposed to be the younger " Iluronian *' gran- 
ite contained such cubes in the fluid inclusions, while the *'Laurentian " 
granite did not. Here we have an eruptive granite in a district mapped 
as " Huronian " that so far reveals no salt cubes. Of course, the evidence 
is negative; in another section, or possibly in some overlooked portion 
of this section, they might be found. So long as Mr. Wright has used 
this as a means of diagnosis, we point to the results here simply for 
what they are worth to those who rely upon microscopic analysis only. 
The hornblende is of a green color, and is broken and torn. Consid- 
erable magnetite, pyrite, and secondary hematite was seen. Some mi- 
nute crystals and grains, supposed to be zircons, were also observed, as 
well as secondary epidote. Titanite is quite abundant. The granitef 
at the mouth of Dead River (62, G3) is seen microscopically to be simi- 
lar to the one just described {*^(^). Its feldspar is not so much decom- 
posed, and the orthoclase and plagioclase are readily distinguishable, 
the latter being quite abundant. The hornblende has been almost en- 
tirely altered to chlorite and biotite (1). The quartz contains microlites 

and fluid and vapor cavities. Some minute crystals of zircon were seen 
in the feldspar as well as in the quartz. The decomposed feldspar is 
almost filled with microlites. Epidote is abundant as a secondary pro- 
duct. The rock also contains magnetite. 

Specimen 82 (p. 52) is a pinkish-gray granite. Under the micro- 
scope it is seen to be composed of orthoclasc, plagioclase, quartz, biotite, 
muscovite, and magnetite. The feldspar is fresher than in the preced- 
ing granites, and contains numerous mica inclusions, mostly muscovite. 
The qnai'tz holds microlites and both glass and stone cavities. The 
muscovite generally cuts through or is mortised into the biotite, the 
same as the feldspar is in the augite of the diabases. The musco- 

* Geol. of Wise, III. 601. 

f Cliloritic gneiss of Brooks. Geol. of Wise, HI. 662. 






vite is quite subordinate to the biotite, and the plagioclase to the 
orthoclase. The red granite youth of Ishpeming (No. 194, p. 55) is 
composed of orthochise, pkigioclase, quartz, viridite, magnetite, and 
hematite. The feldspar is somewhat altered, the plagioclase showing 
the same microlites and hematite alteration products as the orthoclase. 
Part of the feldspar shows very beautifidly the polarization characters of 
microcline. The original mica in the rock is now altered to a viriditic 
material. The quartz contains inclusions of feldspar, biotite, microlites, 
magnetite, and fluid, vapor, glass, and stone cavities. The gneiss, in which 
this last granite is eruptive, is a dark gray foliated rock (192, 193) com- 
posed of biotite, quartz, orthoclase, plagioclase, -magnetite, and a little 
pyrite. The feldspar is much decomposed, and contains microlites, 
as well as the lenticular, colorless foliar, so common in the decomposed 
feldspars in the granites of this region, which we suppose belong to mus- 
covite. The quartz contains the same little disks, as well as fluid and 
vapor cavities. Numerous microlites of apatite, as well as some grains 
that may belong to zircon, occur in the rock. The characters of the 
rock appear rather to bo those of an eruptive than of a sedimentary one; 
but as its relations to anything older than itself were not determined, 
nothing definite can be said upon this point. In a section made of an 
intrusion of the granite through the gneiss (195), both show their re- 
spective characters as given above. 

One half-mile southwest of Huniboldt the granite is intrusive in a 
mica schist. The granite at this point is white, and not of the usual 
pinkish color. Southeast of the Old Washington mine the pinkish gran- 
ite (323) was found intrusive in a hornblendic gneiss. We have termed 
these rocks granite because the foliation appears to be a fluidal struc- 
ture parallel to the contact planes, and because they pass into regu- 
larly non-foliated granites at a distance from their junction with the 

Southeast of the Champion mine the granite (350, 351) is found in- 
trusive in a schist (349, 352, 353, 354). The schist is indurated and 
much changed where the intrusive tongues of granite enter it (347). 
There can be no question that the granite is intrusive, and younger than 
the schists. They have both been mapped by Mr. Brooks as " Lanren- 
tian." Four hundred feet east occur his Huronian magnetic schists 
(348), having exactly the same strike and dip as the schists in contact 
with the granite. Furthermore, if we could prolong the magnetic 
schists in the line of their strike, so far as we coidd ascertain, the non- 
magnetic schists would be included directly in them as a component 



part. The difference now between the two rocks is perhaps due to the 
action of the granite upon the schist. Microscopically this schist (353) 
is composed of biotite, quartz, magnetite, and a niiiscovitedike mineral. 
The quartz contains inclusions of the other minerals, and fluid cavities 
with bubbles in exceedingly active motion compared with the usual rate 
of movement. The fluid cavities are not numerous. The part filled 
with quartz and the muscovite-like mineral appears to be a portion of 
the original fine sediment (mud) that held the coarser material. The 
alteration and crystallization of this argillaceous detritus give with the 
original quartz grains the present texture, approaching closely a gneiss. 

East of the same mine the gneiss (344) was found dipping N. GO'' 
W. 67°, and is finely foliated. This gneiss is cut through by intrusive 
granite, and by dikes of diabase and ''diorite" (343, 345, 34G). The 
latter cut the granite as well as the gneiss. (Sec page 45.) The gneiss 
is composed of biotite, quartz, and the same muscovitedike mineral as tiie 
schist. No. 353, which in fact it closely resembles. The quartz con- 
tains microlites, scales, and grains of the other minerals and fluid cavi- 
ties. The same decomposed material cementing the quartz grains is 
found in this as in the schist. So far as we can tell by microscopic ob- 
servation, we regard this rock as sedimentary, and perhaps only a more 
highly nu^tamorphosed condition of tlie adjacent schist. As its relations 
to any rock older than itself were not observed, of course no definite 
statement can be made. The supposed sedimentary material forming 
the cement and the base out of which the mica, in part at least, has 
crystallized, can arise from the decomposition of feldspar crystals in 
their original position, and a material nndistinguishable from it is seen 
frequently to have been formed thus in eruptive rocks. We base our 
conclusion that the rock is sedimentary upon the general structure of 
the rock, especially upon the form and relations of the quartz grains to 

the rest of the constituents. 

The term quartzite is, we believe, when employed in its proper use, 
restricted t'> an indurated sandstone, and in this sense we employ it. 
We believe this to be more in accordance with the generally accepted 
use of the term, although, in practice, Messrs. Zirkel, Lasaulx, Hawes 
(a pupil of Lasaulx), and other lithologists, employ it also to designate 
quartz veinstones and other forms of chemically deposited quartz. ' Dr. 
Wichmann, it would seem, employed it only for rocks which have no in- 
terstitial or cementing substance remaining imcrystallized between the 
quartz grains, lie classes them under the head of non-fragmental rocks, 
saying that his other class comprises all those " which have been formed 



mechanically out of the materials of older rocks," yet lie describes a 
quarizitc that he regards as having been a fragmcntal rock. In fact, 
his lines between fragmcntal and non-fragment al rocks seem to have 
been drawn from the realms of fancy, as a large proportion of his non- 
fragmental rocks are evidently, both from field and microscopic charac- 
ters, as truly sedimentary as those classed as fragmcntal ones. If wo 
understand Dr. Wichmann aright, we presume that the St. Peters 
sandstone when indurated, as we have frequently seen it, would form a 
quartzite, while the Potsdam sandstone, if it were indurated in hke 
manner, would form a — sandstone, unless some of it had its cement- 
ing material entirely crystallized.* 

The reddish and grayish quartzite, near the northern railroad track 
west of Ishpeming, is composed of quartz in rounded grains held by a 
chloritic cementing material. Considerable hematite was observed as a 
decomposition product. The quartz contains microlitcs, trichites, and 
fluid cavities. The quartzite forming the fall e?i wall of the New York 
mine (18G) is a very dark greenish-gray rock, composed of rounded 
grains of quartz, and crystals and fragments of magnetite cemented by a 
chloritic material. The interstitial substance in this appears to have 
been entirely changed to chlorite. The quartz contains microlites, tri- 
chites, and fluid inclusions more abundantly than the rock last men- 
tioned. A fragment of jasjjer was observed in this rock. Another 
specimen of the same rock (187) is composed of macroscopi^ally evi- 
dent fragments of jasper and magnetite, and quartz grains. Under the 
microscope the section was seen to be composed of quartz, jasper, magnet- 
ite, and chlorite. The quartz has the same inclusions, but part of the 
microlites appear to be zircon. These rocks, as we have before pointed 
out, were evidently derived fi'om the underlying ore-bed (pnge 30). 

The (quartzite (1*J7, 1"J8) found to be older than the intrusive " Lau- 
rentian" granite (page 55) is a dark gray rock composed of quartz 
grains, biotite, and fibrous microlitic cementing material. The quartz 
contains fluid inclusions and little crystals of zircon. The crystals of 
zircon arc the same as tliose observed in the gneiss in that vicinity 
(193), and it is not improbable tliat the quartzite is derived from it. la 
this case the order of succession is, 1st, the gneiss; 2d, the quartzite; 
3d, the eruptive red granite (gneiss of Mr. Brooks). 

The quartzite overlying the ore at the north pit of the Jackson mine 
at Negaunco is made up of the ruins of the underlying ore. It is com- 
posed of quartz, jasper, magnetite, hematite, and a fibrous microlitio 

* Gcol. onVisc, III. 613, Glil, 619, 655. 



interstitial material. The quartz contains inicrolites and fluid inclu- 

The rock through which the "diorite" (page 43, No. 232) passes, is a 
highly indurated feldspathic sandstone (233), in which the feldspar pre- 
dominates greatly over the quartz. It has a greenish, compact, felsitic 
base, holding grains of quartz. This woidd easily pass for a quartz por- 
phyry or felsite, "with those who advocate the passage of sedimentary 
rocks into felsite. It is best classified as a poroditeJ^ Microscopically 
it is seen to be composed of fragments of feldspar with some quartz 
grains. The feldspar is decomposed greatly, forming micaceous scales, 
but shows in some eases its triclinie character. It was most probably 
formed from the detritus of a granite. 

Potsdam Sandstone. 

The sandstones at Marquette resting upon the azoic schists are in 
the upper portions fine-grained (14, 15), but below they become con- 
glomeritic. The coarser sandstone (12 a, 13) is composed principally 
of quartz and feldspar ; the feldspar is the pinkish variety belonging to 
the azoic granites in the vicinity. Many of the quartz grains arc seen 
to be crystals with unworn facets ; it is therefore probable that they 
came from veins, and the sandstone making was quite rapid. The other 
sources of the quartz were probably the granites and quartzites un- 
derlying them. Coarse pebbles occur in portions of the rock belonging 
to the adjacent formations : qmirtzite, ferruginous quartzite, argillite, 
chlorite, -diorite," etc. (IG, 17, 18, 19, 20, 21, 22, 23, 24, 25). Tho 
inclosed pebbles were evidently when deposited nearly, if not quite, in 
the same condition as they and the rocks from which they were derived 
are to-day ; as was pointed out by Foster and Whitney. South of the 
Carp River, in the locality figured by Messrs. Foster and Wliitney, tlio 
sandstone strata are seen to abut against and overlie the vertical edges 
of the quartzite (29, 30, 31, 32, 33, 34). The dip was about S. 20° W. 
IG'^ to 18", The Sandstone at Presq\ie Isle contains the same materials 
as that south of Marquette, but has sufi'ered a local modification described 
in connection with the peridotite of that point; — to which wc now pass. 

Peridotite and Serpentine. 

The chief rock at Presque Isle, north of Dead Uiver, is a peridotic 
one, composed of olivine, enstatite, and diallage, which is the composition 

* Bull. Mus. Comp. Zoology, V. 280. 




of llicrzolite. In places, this rock is much altered, formhig a serpentine 
(G5, C)^, G7, 68, 69, 70, 71, 72, 73, 74). We find every gradation, from 
the rock only partly altered to that which is so completely changed to 
serpentine that only traces of the enstatite, diallage, and oUvine remain. 

Under the microscope, the rock (05) is seen to bo made up of rounded 
grains and crystals of olivine, held in and often completely surrounded 
by tlie enstatite and diallage. These minerals evidently crystallized later 
than tlie olivine, and play the same role hero that the angito does in dia- 
base, the glass in basalt, and quartz in granite. The olivine is traversed 
by fissures, along which the usual serpontinous alteration has taken place. 
In many, the alteration is confined to the vicinity of the fissures and the 
periphery of the ohvine, but others are changed throughout. Much 
bhick dust comes in the altered portions (magnetite?), as a residue 
left over in the decomposition of the olivine and the formation of the 
serpentine. In many cases this black residuum forms a rectangular or 
irregular network or grating throughout the changed olivine. The 
enstatite is altered along the cleavage planes and network of fissures 
by which it is traversed. It does not become changed to the serpentine 
so readily as the olivine. All contain inclusions of black octahedral 
crystals that are presumably magnetite, as the powder is magnetic, and 
no trace of chromic oxide was found by chemical tests. Besides the ser- 
peutinc, there occur, as other alteration products, feldspar (1), viridite, 
and dolomite (1). The hand specimen {G5) is a grayish black (almost 
black) rock, showing under the glass a little serpentine, enstatite, and 
magnetite. It weathers somewhat brownish. 

In other specimens from the same rock, but more altered, we only 
find traces of the original structure. The formation of the serpentine 
along the fissures, and the network of magnetite, usually arc well marked 
after the enstatite, diallage, and olivine are entirely altered. The serpen- 
tine, unless it suffei* alteration itself, generally shows under the microscope 
its original structure, as it was formed along the fissures. One section 
(71) shows simply greenish pseudomorphs after olivine enclosed in a car- 
bonate, presumably dolomite. Another section (74) is composed now of 
serpentine and magnetite, and, if it were not absolutely known whence 
it came, its derivation could only bo told by the arrangement of the mag- 
netite. Certain of the specimens are largely composed of the dolomite 
observed in No. 71, and microscopic as well as field examination renders 
it most probable that Dr. Rominger's stratified dolomite (72) is simply 
a more highly altered portion of the peridotite. No. 71 came from the 
east side and out of the same upper formation as No. 72. This is a 




reddish brown and greenish serpentine, traversed by a fine network of 
doloraitic veins. The mieroscopic charaeters of the decomposed pcrido- 
tite were given to some extent by Dr. Wiehmann, who, it wonld seem, 
had only the serpentine, under which name he describes the rock.* 

The geological history of tliis rock is very interesting. Dr. Houghton 
thought that it was an eruptive rock, and younger than the sandstone 
which was uplifted by it, believing it to be a greenstone impregnated 
with serpentine. He states that, near the line of junction, the sedi- 
mentary rock has been greatly shattered, and its fissures filled with 
injections of calcareous matter. Dr. John Locke thought the ''light 
green trap " was interfused with the sandstone at this point. 

Messrs Foster and Whitney considered that the rock was an immense 
consolidated lava flow, although it wanted the vesicular structure, while 
the part filled with the white veins was regarded as a volcanic sand or 
ash deposited on the lava stream. Younger than this azoic lava was the 
sandstone deposited upon it (Potsdam). Chemical analysis was given of 
it, but no name assigned to the rock. Later, this was regarded as 
closely related to serpentine by Professor Whitney, who gave three 
analyses of it.f Later, Dr. Hunt, accepting Professor Whitney's analy- 
ses, regarded this rock as a somewhat impure sedimentary serpentine 

belonging to the Huronian series. 

Dr. Rominger later regarded this rock as a half decomposed basalt or 
highly ferruginous serpentine ; the part filled with the veins was taken 
to\e an older sedimentary rock, a dolomite, upheaved and broken by 
the trap, and overlaid by the conglomerate and sandstone. This sand- 
stone is supposed to have been deposited in tho inequalities of tho 
underlying rock following its contours. He thought it most probablo 
that the sandstone was deposited at its present inclination, although it 
may have been slightly upheaved since. The conglomerate beds at the 
base of the sandstone arc said to contain mimerous fragments of the un- 
derlying rock. We regard this pcridotite as an eruptive rock, younger 
than the sandstone overlying it, and agree in this particular with Dr. 
ITougltton. The portion filled with veins, that was taken by him as 
a sedimentary rock belonging to the sandstone, or a mixture of sand- 
stone and trap ; as a volcanic sand or ash, by Messrs. Foster and Wliit- 
ncy; and as a dolomite, older than both the trap and sandstone, by Dr. 
Eominger,— we regard as simply the upper portion of the intrusive mass 
modified by its contact while heated with the overlying sandstone, and 
by the percolating waters since. 

* Gcol. of Wise, HL 619. 

t Am. Jour. Sci., 1859, (2,) XXYHI. 18. 




As we differ so strikingly in most particulars from the geologists 
quoted, it is necessary to give our reasons therefor. Only part of a day 
could be spent at Presque Isle ; therefore, many things that ought to 
have been examined could not be. On the southeastern side, the sand- 
stone dips quite irregularly from twenty to thirty degrees southerly. The 
strata follow the curve of the underlying peridotite, fonuing in places 
anticlinals. The distinction between the sandstone and its underlying 
rock was everywhere seen by us to be well marked. The surface of the 
peridotite is in rounded knobs, the whole mass itself in general outline 
forming one iunncnsc knob. The sandstone and conglomerate were ex- 
amined, and found to conform in their stratification to the contour of the 
whole mass, having the same waving outline; also, for from two to three 
feet above the peridotite, they are indurated, changed, and show charac- 
ters that we regard as evidence of heat action and of hot waters. They 
arc filled with vein and chalccdonic quartz, and hardened and reddened 
the same as is the sandstone immediately underlying the melaphyr over- 
flows in the Copper district (75, 76, 77, 78, 79). Certain portions have been 
changed, so that they resemble a volcanic ash, although they are simple 
ferruginous sandstones (78). Above the limit of baked sandstone and con- 
glomerate comes the unaltered ordinary red sandstone (81). Microscopic 
sections of the indurated conglomeritic sandstone show that much of the 
quartz is a secondary water deposit since the deposition of the fragments 
composing the rock. We searched carefully for the pebbles or fragments 
of the underlying rock in the conglomerate, which Dr. Rominger states 
are abundant, but could find none. We have been unable to find cither 
macroscopically or microscopically a single trace, so fiir, of the peridotite 
or of its veined portion (doUanite of Rominger) in the conglomerate or 
sandstone. The peridotite forms abundant pebbles now upon the beach, 
which, had the conglomerate been formed upon it, should have been 
included. The conglomerate and sandstone contain the same material 
in pebbles, etc. that the' sandstone and conglomerate do in the Mar- 
quette quarries and near Carp Rivor. Had the sandstone and conglom- 
erate been laid down upon the irregular surface of the peridotite, they 
should have abutted against its unconformable portions, the same as 
they do against the quartzite at Carp River; instead of this, the strata 
conform to the curves of the peridotite, like layers of blankets, forming 
anticlinals and synclinals. The dip in many places, especially on the 
southeastern side, is too steep and irregular, while the strata are con- 
tinuous, to have been formed at that angle by sedimentation. The 
induration of the sandstone and conglomerate, and of the enclosed peb- 





bles, as well as the deposition of the silica, do not occur where the 
sandstone has been seen to come in contact with the "Iluronian'* 
schists and quartzites. From the above facts we feel that we arc justi- 
fied in dissenting from the views of most of those who have written 
upon this locality. 

At the eastern portion of Presque Isle, either a fault or a protrusion of 
the peridotite up through the sandstone exists. This locality we were 
able to examine only a minute or two, on account of an approaching 
thunder-storm, while we were in a row-boat, but it deserves further care- 
ful examination. The best serpentine that we saw upon Presque Isle was 
observed at this place. In the thin section, the more serpcntinons 
portions of the peridotite are frequently seen to contain dolomite, and 
fragments effervesce freely in hot iiydrochloric acid. The upper portion, 
supposed to be dolomite by Rominger, extends as a sheet of variable 
thickness over all the peridotite separating it from the overlying sand- 
stone. This, so far as we can tell, is the upper portion of the peridotite, af- 
fected by direct contact with the sandstone, and by the action of hot waters 
since, at the time the silica was deposited in the conglomerate. This 
part is fdled in with impure dolomitic veins, which, it seems, caused Dr. 
Rominger to pronounce the rock a dolomite, although the veins have 
the characters of being secondary water deposits, as they were described 
by Messrs. Foster and Whitney, and not igneous injections, as they were 
thought to be by Dr. Houghton. The unmistakable peridotite has in 
places the same structure. The peridotite is much fissured, breaking up 
into rounded masses, cemented by segregated serpentine. We regard, 
the peridotite as eruptive, and feel that its field and microscopic charac- 
ters both point to the same conclusion. The manner of eruption was 
probably something like the laccolites described by Mr. G. K. Gilbert; 
on the sides the strata were arched and bent upwards, but on the eastern 
end either a fault or protrusion exists. This place would afford an 
excellent chance to study the relations of the sandstone to the peridotite, 
if the contact of the two can be seen. 

If we are right in our observations and conclusions, this locality has 
an important bearing upon the origin of the serpentine here, showing 
that it is a metamorphosed eruptive rock, and of younger age than at 
least some one hundred feet of the sandstone. It further shows that, 
so far as this is concerned, lithology fails in giving the age of a rock, 
this having been indorsed as good '^ Huronian" ;* also that an eruptive 

* Mr. Brooks thinks "it is not certain that this is of Huronian age." (Gool. of 
Wise, III. 659.) 



rock may be so changed as to be taken by observers for a sedimentary 
stratified one, even a good dolomitio limestone. The origin of the scr- 
pentinoLis part by direct change in sUa of a peridotite (eruptive), as well 
as by the filling of fissures iu the peridotite by serpcntinous material 
derived from the surrounding rock, would seem in the main to be 
consonant with the observations of Bonney, Bccke, Berwerth, Dathc, 
Doelter, Drasche, lioehstetter, Koch, Lemberg, Sandberger, Strong, 
Tschcnnak, Zirkcl, and others. Peridotite, wdiich we provisionally 
classed with gabbro under basalt, in a preliminary publication ''On the 
Classification of Rocks,"* it would seem from further and more extended 
study, should be classed as a distinct species ; and some other rocks 
may possibly belong with it. This species would represent a more basic 
one than basalt, containing generally between thirty-five and forty-five 
per cent of silica, or, more nearly, forty to forty-three per cent. The 
reasons for this view it is intended to give fully in another publication, 

but they would be out of place here. 

The following analyses (incomplete) of this peridotite were made and 

published by Prof. Whitney : — 











with tbe iron. 










28. G7 






Analysis!, is taken from Foster and Whitney's Peport on the Geology 
of Lake Superior, 11. 92. Analyses II., IIL, and IV., from the Ameri- 
can Journal of Science, (2,) XXVIII. 18. 

Tliree miles and a half noiihwest of Ishpcming, or one mile and a half 
west of Deer Lake, serpentine occnrs abundently on the land of Mr. 
Julius Ropes, postmaster of Ishpeming.f This rock, altliough quite 
hard, forms very l)eautiful specimens when polished (234, 235, 23C, 237, 

* Bull. Mus. Comp. Zoology, V. 279. 
t First Annn;d Ecport of ilio Couuiussioncr 
Midiigaii, pp. 204-200. 

VOL. VII. — NO. 1. 

of Mineral Statistics of the State of 




238, 239, 240, 241, 242, 243, 244, 245, 246). Associated with and 
comprising probably part of the same formation is a greenish and grayish 
limestone (247, 248, 249, 250, 251). In one place much chrysotile was 
seen, which had formerly been regarded as asbestus (252), 

No. 235 is a beautiful green serpentine, giving a colorless section 
holding magnetite. Under the microscope this shows a most beautiful 
fibrous aggregate polarization. Other sections (241, 242, 243, 245) 
show a more coarsely fibrous aggregate polarization, and arc composed 
of serpentine and magnetite. The magnetite is scon here to be arranged 
in the same way that it was in the more decomposed peridotite of Presque 
Isle, forming a network corresponding to the outlines of the grains and 
fissures in the olivine, as well as occasionally a network in the altered 
olivine itself. Although we find no trace of either olivine or cnstatitc in 
this serpentine, this structure gives a strong probabiHty that this rock 
was originally in nature and origin a peridotite. Every microscopic 
character in this serpentine indicates that it is formed by direct altera- 
tion in situ from another rock, and, so far as wc can now tell, that was 
an olivine one. Whether this is of the same age and origin as that at 
Presque Isle or not can only be detci'mincd, if at all, by studying its 
relations to its associated rocks. 

General Discussion and Results, 

The historical part of this paper we have endeavored to bring down 
to the date of its completion. As the historical portions of both the 
Iron and Copper districts were, in the main, written in 1879, the lat- 
ter material has been added as best it could be done. «0n March 6, 
1880, through the courtesy of Prof. T. C. Chamberlain, Chief Geolo- 
gist of the Wisconsin Survey, we received an advance copy of that por- 
tion of the third volume of his survey publications which gives Dr. 
Arthur Wichmann's microscopic analyses of some of the ro';ks in the 
Iron district and Appendices A and B, or from pages GOO to 6G3. 
This detached portion has been referred to repeatedly in the preceding 
pages, but no connected account was or need be given of it. On April 8 
the complete volume was received, but as the preceding portion of our 
work was, with the exception of a few pages, already prepared for the 
press, and in part struck off, it became necessary to incorporate all 

mention of it in this portion of the paper at this date (April 10, 


The observations and figures given in the preceding text show conclu- 
sively that the statements of Messrs. Dana, Kimball, Hunt, Brooks, and 




others, that the iron ore is intcrstratificd in the associated schists, 
are incorrect, and only return to the view advocated by Mr. Foster in 
his early publication. So i'nv as geological science has now advanced, 
the facts observed can only be explained by the eruptive origin of both 
the ore and jasper, as they make the same formation. The only escape 
from this conclusion is the supposition that the ore and jasper have been 
rendered plastic 1)1 situ, while the chloritic schist has not been. Such a 
supposition Mr. Brooks was forced in part to adopt.* That the ore and 
jasper have been thus rendered plastic, while the schists, quartzites, and 
other associated rocks have not been, is too absurd, chemically or geo- 
logically, to be tolerated for a moment as an hypothesis. Should it or 
any other theory be proved to be correct in actual fact, then it is to be 
admitted ; but when one resorts to theories that are not sound scientifi- 
cally, merely to escape from a dilemma that a former theory brings him 
to, he is neither philosophical nor scientific. Theories must conform to 
facts, not the facts to the theory. We can point out facts whether they 
can be explained or not, but the theory must conform to our present 
knowledge. The ore and jasper show that they are the intrusive bodies 
by their breaking across the lamination of the schists and other rocks, by 
the changes that take place in the latter at the line of junction, by horses 
of schist being enclosed in the ore, by the curvature of the lamination 
produced by the intrusion of the ore and jasper, etc. Not the slightest 
sign of the plasticity or intrusion of the schists relative to the ore or 
jasper was seen. That the present lamination of the schist existed prior 
to the intrusion of the ore and jasper is shown by the effect of the latter 
upon and its relations to it. That this lamination is the original plane 
of deposition is for part of the schists not known; but whether it is or 
not, it has been taken to be such by tlie observers quoted in .the estab- 
lishment of their theories, and they must abide by it. The lamination, 
however, coincides with many of the well-stratified rocks adjacent, and 
in some of these the ore and jasper were unmistakably intrusive. The 
schists that retained well-marked stratification planes showed in some 
places extraordinary contortions, one specimen (293) showing a syn- 
clinal and anticlinal fold, requiring, were the top eroded, the counting 
of the same layer four times in the width of two inches. This is only 
one case out of numerous ones observed (292, 292+, 302). In the fine- 
grained detritus composing some of the schists it is quite likely true that 
the lamination does not coincide with the original bedding ; but if it docs 
not, then the breaking of the ore across any chosen plane whatsoever, 

* Geol. ofMioh., I. 139, 140. 







except tlie lamination plane, can be shown more easily than in the for- 

mer case. 

The ore and jasper seem to have been erupted in huge bosses and 
overflows, as well as intruded into the schist in the form of long arm- 
and wedgc-likc masses or sheets. On account of the banded character 
of the jasper, and the intrusion generally being nearly in line of the lami- 
nation in the large mass, they have an apparently stratified character 
to those who believe any " striped" rock is a sedimentary one; but when 
examined in detail, and in places where the relations can be seen, they 
prove to be eruptive. Those who advocate the sedimentary origin only, 
take the jasper and ore as a whole, and, because it is apparently to them 
stratified^ assume without further question or examination that it is so. 
We have gone upon the principle, that the relations of rocks to one an- 
other show the origin of each one except the oldest, and this must be 
the arbiter in every case when the other characters are doubtful or are 
quc!^^ioned, It happens then that this is largely a question of methods 
and principles of observation. 

The natural work of mining is to obscure or destroy the geological 
evidences; furthermore, the natural changes that have taken place in 
the constitution of the rocks, the decomposition, the uplifts, fractinxs, 
foldings, and other accidents which they all have suffered, tend to in- 
crease the difficulty of finding such proof. Of necessity the characters 
show best upon the walls of abandoned open pits which the rain had 
washed clean, but they were also found in the present workings. Like- 
wise they are best studied in comparatively small masses, partly because 
their relations are easier seen, and partly because the miner generally 
leaves no others that can be studied. We were enabled, however, to 
observe the intrusive rehitions, not only of small masses, but of some 
containing thousands of tons. The small masses were, however, either 
seen to be joined, or had been joined until cut off by mining, to the main 
body. The view that they have been rendered plastic in situ is not sus- 
tained by the facts, and when we take into consideration the associated 
rocks is absurd on its face. The facts, then, sustain the views and ob- 


servations of Messrs. Foster and Whitney, and :'.how that the work of 
the other observers has been superficial and inaccurate. We are 
well aware that objections from a metallurgical or chemical stand- 
point have been raised against the theory of the eruptive origin of 
hematite and silica together, in such forms as we now find them. If the 
ore was magnetic at the time of eruption, and has since been altered, 
this objection is then done away with. The secondary changes that 






« * 



have occurred in the rock since eruption, as shown by microscopic exam- 
ination, may also help. It is well known that there are facts in every 
science that it is not able to explain at any one given time ; but the 
flicts exist the same, and the science in time rises to meet them. So in 
tills case the fact is they are eruptive, and the burden of chemical ex- 
planation rests upon tlie chemist, not upon us. He must explain it 
sooner or later, unless he disproves our observations. Crystals of hema- 
tite crystallizing from the molten magma of trachytes and rhyolites 
have long been known, and are described in all the standard woH^s 
on micro-lithology. These then offer the same problem, and prove that 
hematite can be crystallized directly out of the same molten magma, 
and at the same time with the silica and silicates. It is the business of 
the chemist to meet the fVicts, and not for us to make the facts con- 
form to his knowledge or tlieories. It is our business to state what we 
see and find, and his to explain it if he can, but not to deny it for the 
simple and sole reason that he cannot cope with it in the present state 
of his knowledge. The eruptive origin of the iron also has a bearing on 
the theory that its presence indicated a vast amount of organic life in 

the *'lIuronian" epoch. 

We have found that a large proportion of the rocks said to be inter- 
stratified, and to pass by insensible (or any other) transitions into the 
adjaeeut rocks, are eruptive, and do not so pass into the country rock. 
The assumption that they were stratified was based on their foliation 
being parallel to their walls, on their being intrusive approximately par- 
allel to the lamination of the schists, their general resemblance to the 
country rock of similar chemical composition, the inability of the observ- 
ers to find their lines of junction, and the lack of knowledge of the same 
observers of the characters of eruptive as well as of sedimentary rocks. 
Their decision in this, as before, was based on a mere superficial glance 
over the surface, and the assumption that, because a rock looked as 
though it was stratified, i. e. had any marks that they thought indicated 
stratification, it must of necessity be stratified. No elTort was made to 
find out the real relations of the rocks to one another. No attempt 
was made to see whether one rock was laid down on another as a sedi- 
mentary bed, or whether it was an overflow or intrusion. They were 
''striped" or foliated, jointed or showed cleavage planes, and that was 
enough ; any further observation was superfluous. They assumed that 
Messrs. Foster and Whitney's work was erroneous without making the 
necessary observations to prove it so, and the geological world accepted 
it without question because it agreed with the fashionable theories. 




The intrusive rocks belong in general to the basalts^ but arc of course 
old, and in the majority of cases greatly altered. One probable ande- 
site as well as intrusive felsites (rhyolites) was discovered. These rocks 
had never been noted before by the previous observers. One class 
of the intrusive rocks can be referred to the basalts only with doubt, as 
the necessary proof of their original composition is thus far wanting, 
i. e. the actinolite rocks. The evidence is very strong that in the other 
basic intrusives all the varieties are produced by the alteration of their 
constituents, and that they were not erupted in their present state. 

It is to be noticed that, while we have found olivine abundantly in the 
diabases, Dr. Wichmann states that " olivine diabase is not present 
amongst the rocks from the iron, region of Lake Superior."* 

The " soft hematites" arc doubtless produced by the decomposition of 
the jasper and its ore, brought about by the fracturing of the rocks by 
the intrusives and by the secondary action of water, presumably hot, 
on account of the microscopic characters of the quartz deposited by it. 
Besides the *' soft hematites" there occur the quartzites and conglom- 
erates derived from the ore and jasper, as well as the sandstones and 
schists impregnated by iron, which are sometimes mined to a slight ex- 

We have heretofore seen that the view that the " Huronian " uncon- 
formably overlies the " Laurentian " has been only supported by the 
fact that the foliation of the latter did not conform in its dip to the 
lamination of the former. This proof is of no value unless it can bo 
shown that both rocks are stratified and in situ. That the latter is not 
so, we have seen in numerous localities. Heretofore the two systems 
have not been observed in contact, but recently statements have been 
published that their junctions have been seen in other regions.t The 
statement is made that both rocks are stratified, but no proof is adduced 
to show on what the conclusion is founded, and, although the contacts 
were said to show beautifully, nothing was published indicating that the 
kind and manner of the junction was observed. It woiild seem that 
even here the decision concerning the unconforma})ility was based on 

the foliation only. 

So far as the Marquette district is concerned we have shown very 
much stronger and more abundant evidence to prove that the " Lauren- 
tian " granite is younger than the '^Huronian," and an eruptive rock, than 
has been advanced by Mr. Brooks (the only one who has advanced any- 
thing called proof) to show that it is older. Further, the inability of the 

* Geol. of Wise, III. 627. 

t Ibid., III. 98, 108, 117. 



later observeris to distinguisli the eruptive rocks, even in the " Iluro- 
nian," detracts from their evidence concerning the " Laurentian." The 
granite that Mr. Brooks phiccd as Formation XX. of the '* Huronian/' 
merely because that was the easiest way to dispose of it, unless he 
wished to acknowledge that his *' Laurentian" granite or gneiss was in- 
trusive in the '* Iluronian," bids fair to absorb now all the " Laurentiau" 
region, if we can judge from what Mr. Brooks writes. He says: "Dr. 
llominger considers certain granitic and gneissoid rocks north and south- 
west of Marquette, which 1 did not study but regarded as Laurentian, 
to belong to tliis series. I have but little doubt but that the younger 
Iluronian rock made out in the Menominee region (the granitic bed 
XX.) will yet be identified in the Manpiette region, and will be found to 
bo more or less gucissic. The very rocks mentioned above may pos- 
sibly be Upper Huronian ; the granites, etc., southwest of Michigannno 
lake very probably are."* Although this granite is in the region mapped 
as '^ Laurentian" by Mr. Brooks, he does not tell us how to separate it 
from tlie *' Laurentian," or where the dividing line is to be found. How 
does he know that it is not the same as the other "Laurentian" rocks? 
He has never made any examination to see whether it is or not, and 
in the above-quoted remark of his he virtually acknowledges tliat he 
know nothing of the rocks that he mapped as "Laurentian" in the 
district since examined by Dr. Bominger. 

We tried to find some point where we could trace rock continuously 
from well marked and mapped "Laurentian" into the "Huronian," but 
were unable, with the time and opportunity at our disposal, to do more 
in that direction than we have already pointed out. The evidence is 
strong, but not so conclusive as we could have wished; yet what would 
it have availed us if we had found such a locality? We should have 
been told :. " Oh ! that is Formation XX. that you found ; we knew 
nothing about the region, so we mapped it as Laurentian." May we 
suggest that hereafter geological maps of Lake Superior be colored as 
"Iluronian," and "Formation XX." 1 Let us substitute the last term 
for the " Laurentian " at once, and have done with it before Formation 
XXIL is born. At another locality, the granite that Mr. Brooks as- 
signs to "Formation XX," Professor Irving places under the "Kewee- 


While at Lake Superior the followers of Dr. Hunt thus place a 

troublesome granite cutting the '* Huronian" as the latest formation 

in it (except one), in Eastern I^Iassachusetts a granite said to cut and 



* Geol. of Wise, HI. 529, 530. 

t Ibid., HI. 193-195. 



to be intrusive in the Primordial slates, as well as in the "Huronian" 
so called, is for this reason placed by them at the base of the '* Huro- 
nian." Furthermore,"the diabases that are i^itruslvc in all, even the 
youngest rocks known here, arc for that reason considered to be the 
equivalents of the '^ Norian," and regarded as older than the " Huro- 
nian." Now, if the granites are intrusive in the Primordial or Eraintree 
slates, as we know the felsites are intrusive in the granites, and as we 
know the diabases are in all, we naturally should, as we have done, 
regard these rocks as crystalline eruptive ones, owing their crystalline 
character to crystalli/ution from the molten magma, and geologically 
younger than the Primordial, i. e. Palaeozoic rocks. But we see now 
that we were mistaken. Why not go to the Cordilleras and say of the 
basalts, These are " Norian " or " Naugus Head"; of the rhyolitcs, These 
are *'Huronian"; of the trachytes and nevadites, These arc " Lauren- 

tian," or "Formation XX. "; of the andesites, 1 Why not station 

one's self by a volcanic crater, and determine, as the eruption takes 
place, whether Formation V., XV., or XX. is rushing by? 

It seems, then, that in different localities different methods of inter- 
preting the same facts are resorted to, but for the same purpose and 
result, — the rocks come out '' Huronian " every time. Taking into 
account the methods pursued ; the hypothesis, yet unproved by any 
careful, accurate work, that lithologiea] evidence is conclusive ; the 
assumption that foliation, banding, etc. of necessity prove stratifica- 
tion ; the practice of inserting faults in the formations wherever it 
becomes convenient to do so in order to carry out the theory ; that Dr. 
Hunt, in order to sustain his views, has, in Eastern Massachusetts, 

directly stated that the granite cuts the felsite, when the reverse is 
exactly the case, dike after dike of the latter cutting the former, as 
pointed out by us before,* and since most conclusively shown by Mr. 
J. S. Diller;t that the Norian rocks are probably in all cases eruptive 
basaltic rocks (gabbros) ; that the Keweenawan system has no founda- 
tion except in erroneous observation, as it conformably overlies the 
Potsdam sandstone, as we shall show later; — 
things into consideration, we feel that the very basis on which the Lau- 
rentian, Huronian, and other such geological epochs were established, is 
yet an open question for discussion. Even in Canada the evidence is 
very far from being clear that the relations of the Laurcntian and Huro- 

taking these and other 

niau are what they are supposed to be. The agreement of hundreds 

* Bull. Mu3. CoTijp. Zool., V. 282. 

t Proc. Bost. Soc. Nat. Hist. XX., 354. 




of geologists in every quarter of the world docs not establish any- 
thin*'-, if that airrceuicnt is based on the same theories and methods, 
unless the theories and methods are correct. The evidence is clear 
enough in New England and at Lake Superior that the theory is un- 
proved, and the methods and observations incorrect or superficial. It 
seems to us that a striking commentary on the value of lithological 
characters is afforded in the Marquette district by the letters and the 
comments upon them given on pages 657 to GGO, inclusive, of the third 
volume of the Geology of Wisconsin. 

We frequently are informed that microscopic analysis will make up 
for all deficiencies in field work; that one can tell in this way whether 
a granite or any other rock is eruptive or metamorphic ; that Formation 
XX. is to be distinguished in this way from the Laurentian granite, 

The study of rocks microscopically enables us to investigate their 
structure, constitution, and alterations, — the structure of their constitu- 
ents and the various relations that these bear to one another, as well as 
the order of their formation. It gives us the internal history of a rock 
more or less complete, — a thing that no other known method will do. 
Jt enables us to tell the species, arrange, and generally to classify our 
rocks. With the exception of such as are greatly altered, it enables us 
to distinguish the fragmental from the non-fragmental forms. When we 
are familiar with the microscopic characters of unchanged sedimentary 
rocks and of unaltered volcanic ones, they having been known to be 
such from field evidence, we have a basis for recognizing rocks, con- 
cerning whose field relations we know nothing, as belonging to one or 
the other of these classes, the same as by the unaided eye we recognize 
a coarse granite or conglomerate. This of course only applies to rocks 
concerning whoso nature and origin there is no dispute; or to those 
which under the microscope show such undoubted evidence of their 
origin that it cannot be rejected. If a rock is clearly seen under the 
microscope to be made up completely of fragments, no one would doubt 
that it was a fragmental rock, even if it looked to the unaided eye as 
thoudi it were a non-fragmental one. In like manner, when a rock has 
the microscopic characters of an eruptive one, we feel that it is right to 
regard it as such, even if it was supposed (not proved) to be a sedimen- 
tary one by the collector in the field. Both of these are of frequent 
occurrence in the work of a lithologist. Take now the gi'cat interme- 
diate class of rocks, those that are so altered that their original charac- 

* Gool. of Wise, IL 73; III. 194, 255. 





ters are greatly or entirely changed, and the case is different. We can 
only proceed in safety when we know their field relations, or those of 
rocks that are like them. In order to know the microscopic characters 
of a sedimentary granite (if such a rock exists), it is necessary to study 
one that is known beyond question to be sedimentary, and to compare 
it with the most highly altered eruptive ones known. By this metixod 
of proceeding, always taking as the basis rocks whose relations to their 
fellows were known, diagnostic points of great value would be found, 
and a more just idea of the relations of the fragmcntal and non-frag- 
mental forms obtained. The field evidence would have to be the 
arbiter in all cases. If a rock is eruptive, or if it is sedimentary, it 
is so, whatever may be its microscopic characters. In this class of 
rocks lithology is at present weak, and assumptions take the place 

of facts. 

Althou^^h in no case in this paper have we attempted to give any 

elaborate microscopic analyses, but only a few of the more general facts, 
we have shown plainly enough the fallacy of determining the geological 
relations of highly altered rocks by microscopic analysis alone. Any 
one who takes pains to read pages 533 to 599, inclusive, of the third 
volume of the Geology of Wisconsin, will doubtless be convinced that 
different observers, under the present method of microscopic analysis 
and classification, reach widely different results in the study even of the 
same specimens. He can further compare our description of the Picnic 
point rocks with that given on page 5G7, and also with Mr. Brooks's state- 
ment that granite dikes "have never been observed in the Marquette 
scries " {I c, p. 452). It is of course worthy of remark, that of the litholo- 
gists who have microscopically studied the rocks of Lake Superior, Messrs. 
Pumpolly, Wright, Irving, Ilawes, Rutlcy, Julien, Tornebohm, and Wich- 
mann, not one, so far as we can learn, had at that time any especial per- 
sonal acquaintance with the characters of modern unaltered eruptive 
rocks, except possibly the two last named. Yet it is essential that one 
should be thoroughly acquainted with the unaltered forms of rocks be- 
. fore attempting to solve the most difficult lithological problems on the 
globe, i. e. those relating to the altered forms. As descriptions of what 
these observers saw in the individual specimens examined by them, their 
work is undoubtedly of great value; but beyond that there is a great 
chance for differences of opinion concerning their conclusions, or the 
basis upon which these were established. 

The sedimentary rocks of the Marquette district generally give evi- 
dence of being shore deposits, and although they may have been deeply 



buried under later formations, yet in themselves we consider that they 
give no evidence of it. 

The general structure of the country would seem to be as follows. 
The schists, sandstones, etc., having been laid down in the usual way, 
were then disturbed by the eruption of the jasper and ore ; this 
formed the knobs of jasper, the banding belonging to the fluidal struc- 
ture, and not to sedimentation. Besides occurring in bosses, the jasper 
was spread out in sheets, and intruded through the rock in wedge- 
shaped masses, sheets, and dikes. Much of the original rock still re- 
mained horizontal, and new sedimentary deposits continued to be formed 
out of the jasper and the other rocks. Next came the eruption of " dio- 
rite," which completed most of the local folding and tilting of the strata. 
Finally, the granite eruption took place on both sides of the. *' Huronian," 
uplifting and contorting the strata near it, and perhaps laterally com- 
pressing the enclosed iron-bearing rocks. No basis exists so far, then, for 
the scheme of formations laid down by Mr. Brooks, as it was founded on 
the supposition that all the rocks were sedimentary. The other results 
of our work are : the showing more clearly the age, origin, and nature 
of the peridotite at Prcsque Isle, and the formation of serpentine from 


it in situ; the finding of ottrelite schist as a metamorphosed rock from 
the ordinary schist; the showing that tourmaline and olivine are more 
abundant here than heretofore known ; the finding of granite and fel- 
site within the Marquette district, etc., etc. 

Concerning the serpentine (peridotite) of Presque Isle Mr. Brooks re- 
marks, "It is probably Huronian, and presents some of the phenomena 
of an eruptive mass." * Later he says, "It is not certain that this is of 
Huronian age." t 

Although in deference to the common custom we have employed the 
term jasper in writing of the silicious eruptive rocks associated with the 
ore, in reality it is not properly called so. It is often uncolored, and 
has then generally been designated by obscrvci's as a quartz schist, they 
believing it to be sedimentary. The rock further has been denominated 
felsitc or petrosilex, but physical and chemical characters remove it from 
these old rhyolitic rocks. It is more acidic than the rhyolites, the silica 
being above eighty per cent. We also found other eruptive rocks of like 
acidic character, and, so far as our observations have now^ gone, it seems 
probable that rocks of this class are much more abimdant than we should 
at first suppose. They would naturally be taken at first sight for 
quartz schists, quartzites, and other sedimentary rocks, and no further 


Gcol. of Wise, III. 532. 

t Ibid., 659. 



investigations bo made to ascertain their relations to the associated 
rocks. We would propose, therefore, that all the acidic eruptive rocks, 
whose chemical and physical constitution carries them above the rbyo- 
lites, should be designated as JaspUites from tao-Trts and Xt^os in accord- 
ance with a suggestion of Professor Whitney. 

Finally, so far as our work has gone, it shows that Messrs. Foster and 
Whitney were right in their observations and conclusions, so far as it 
relates to the geological structure of the country, or to the origin of the 
rocks and ores, except the pcridotitc. To them and to them alone be- 
longs the credit of having done their work accurately, and as thoroughly 
as the circumstances would allow, while the more recent observers 
and writers, Kimball, Credner, Rivot, Hunt, Dana, Brooks, Lesley, Win^ 
chell, Newberry, Wright, and others, have held and pushed tlieories in 
direct opposition to the facts,. until a geologist who took a different view 
was regarded either with pity or derision. As regards the general geol- 
ogy of the country, we feel that Messrs. Foster and Whitney's writings 
remain to-day the best and most accurate exponents. Considering the 
difficulty of exploring the comitry thirty years ago compared with the 
present, it is surprising how much they saw, how accurate their ob- 
servations were, and how little has been added to our knowledge since ; 
also how our knowledge and science have again retrograded, until geol- 
ogists have gone back to the views of Messrs. Houghton, Hubbard, and 

The Copper District. 

The earliest writer to advance any especial views regarding the cop- 
per and its origin, so far as we are aware, was Henry R. Schoolcraft.* 
He considers it probable that the masses of copper about the Onto- 
nagon River were thrown out of volcanoes by volcanic action. The 
mo'lnitains are said to be of granite (Porcupine Mountains) so far as 
observed, and the sandstone to have been upheaved into a nearly vertical 
position at their base by the elevation of the granite. He considers that 
native copper will never be found in sufficient abundance to pay for 
mining, but that probably "valua\)le mines of the sulphuret, the car- 
bonate, and other profitable ores of copper," will be discovered.t 

In 1823, in describing a supposed vein of malachite on Keweenaw 
Point, he concludes " that the entire peninsula consists of a spine of 

Am. Jour. Sci., 1821, (1,) IH. 201-216. Quart. Jour. Sci. and Arts, London, 

1822, XII. 422, 420. 
t See also Senate Papers, 2d Scsa., 17th Aug., 1822, Doc. 5. 





granite, with sandatoucs, amygdaloid, and sccoudaiy trap, deposited 
around its base.'' * 

Dr. John J. Bigsbj regarded the Lake Superior sandstone as being 
most probably of the age of the Old Eed.t Commander H. W, Bay- 
field, in his paper entitled *' Outlines of the Geology of Lake Supcrioi'," J 
regards the hills of Keweenaw Point as formed of syenitic granite, of 
the same character as that at Granite Point, an^l '^tiposes the idea that 
the first-mentioned point is an amygdaloid district. He regards the 
trap and granite as the prior formed rocks, and that the sandstone is 
composed of their debris. This sandstone, which he takes to be Old 
Eed sandstone, is said to have been tilted by a secondary upheaving, or 
subsidence of the granite. 

In Dr. Douglas Houghton's report on the copper of Lake Superior to 
the Secretary of War,§ we find the following statement : "After having 
duly considered the facts which are here presented, I would not hesitate 
to offer, as an opinion, that the trap-rock formation was the original 
source of the masses of copper which have been observed in the country 
bordering on Lake Superior ; and that at the present day, examinations 
for the ores of copper could not be made in that country with hopes of 
success, except in tlie trap-rock itself; which rock is not certainly known 
to exist upon any place upon Lake Superior, other than Kcvveeua 
Point/' The chief ore of copper that he had observed the mala- 
conite, although a small amount of native copper had been seen in 

Dr. Douglas Houghton states, in his first Ileport on the Geology of 
Michigau,|l that the red sandstone '' in the Trap regions of Lake Superior, 
as in the vicinity of the Porcupine Mountains, .... is seen dipping 
irregularly at a high angle from the elevated district of country, and is 
there of a deep reddish4)rown color." He evidently at that time re- 
garded the sandstone as belonging to one formation, from the St. Mary's 
Eivcr to the Porcupine Mountains. 

Dr. Houghton in his Fourth Annual Report on the Geology of Michi- 
gan, If divides the sandstones of Keweenaw Point as follows, going from 

* Am. Jour. Sci., 1824, (],) VIT. 43-49. 

t Quart. Jour. Sci., 1824, XVllL 1-34, 22S-2G9; Am. Jour. Sci., 1824, (1,) 
VIII. 60-88.. 

t Trau^. of the Lit. nnd TTist. Sac. of Quebec, 1829, 1. l-4fi. 

§ ;N"ov. 14, 1831. Discovery of tlio Source of the Mississippi, Henry R. School- 
craft, New York, 1834, pp. 287-292. 

11 Lanman's Hist, of Mich., p. 353. 

H Joint Documents, Mich., 1841, pp. 472-607. 






below upwards : " conglomerate rock," '* mixed conglomerate and sand 
rock," and *' red sandstone and shales." He regards the first as a "trap- 
tuff," and as made up of " rounded masses of greenstone and amygda- 
loidal trap, of which the former make up by far the larger proportion, and 
scarcely a pebble of any other rock than trap, enters into its composition." 
The second is composed of the same materials as the first, and is conform- 
able with it. The only difference is that part of it is made up of sand 
composed of finely comminuted greenstone. The last, or " the red sand- 
stone and shales," he considers to differ widely from the preceding rocks, 
and to be made up of detritus of the granitic and metamorphic rocks, 
containing, however, some sand that appears to be comminuted trap. 
This red sandstone extended, according to Houghton, as far east as 
Grand Island, where it was unconformabiy overlaid by the " Gray Sand 
Eock" (e.g. the material of the Pictured Rocks), which rested upon the 
uplifted edges of the former. It will thus be seen that he had changed 

his views since his first report. 

All these rocks were said to be traversed by dikes injected parallel to 
the bedding, varying in width from fifty to four or five hundred feet. 
He considered that the sedimentary rocks were all deposited prior to 
the injection of the traps, which rocks he finds \erj abundant in the 
conglomerates, and comparatively rare in the red sandstones. Tliese 
dikes pass from a compact greenstone on the southeast side to an amyg- 
daloid on the northwest. He considers _that they were ''in an intense 
State of ignition while in contact with the sedimentary rocks, as is 
clearly shown by the very great changes that have taken place in the 
rocks last alluded to. In fact, I am disposed to refer the origin of much 
of the amygdaloid rock to the fusion of the lower portions of the sedi- 
mentary rocks referred to, for the reason, that as we pass south from 
this junction, the amygdaloid rocks wholly disappear, their place being 
supplied by greenstone; and again so intimately arc they blended, that 
it is frequently impossible to determine where the amygdaloid ceases 
and the upper sedimentary rocks commence. Fragments of the sedi- 
mentary rocks, the characters of which can be clearly recognized, are not 
of rare occurrence, imbedded in the amygdaloid rock, a circumstance 
which although by no means conclusive, should not be overlooked in 
considering this subject. I would not wish to convey the idea that the 
amygdaloid rocks have their origin exclusively from the altered sedimen- 
tary rocks, but simply that the change in the structure of the trap, from 
greenstone to amygdaloid, may and no doubt does depend upon tlie 
proximity of the sedimentary .rocks to the trap, while the latter was in 



■ ■ 

■ ! 



a state of ignition." {I. c, p. 490.) He states tliat the sandstones have 
evidently been deposited in shoal water, ou account of the abundant 
ripple-marks occurring in them. 

Three species of fucoids, tolerably well defined, were said to have 
been found in the red sandstone. The veins are considered to be of a 
date posterior to the uplifting of the beds, and cut across all three of 
the sedimentary rocks and the traps. They are taken as true veins, and 
their mineral contents are said to change in the same vein as the rock 
changes. The gangue is said to be principally quartz with occasional 
calcite, and the ore to bo most abundant at or near the junction of the 
trap and conglomerate. Ho regards this district as being in its general 
characters and in its veins like Cornwall, Conglomerates were noticed 
with a cement of copper, but only in the immediate proximity to con- 
siderable vehis. He conceived the veins " to be veins of sublimation, 
or in other words to be simply filled from below by the metal in a va- 
porous state, and that all the compounds had their origin from copper 
in a native form."* In 1843, he considered that the sandstone cast of 
Keweenaw Bay was older than the Trenton, while the western sand- 
stones and conglomerates were formed during the period in which the 
trap was upheaved, and were probably contempor.aneous with the New 
Ked Sandstoitc.f 

It will be seen here that Dr. Houghton had entirely changed his 
views regarding the relations of the sandstone. In 1841, the sandstone 
of Keweenaw Point was said to be older than the St. Mary*s sand- 
stone; in 1843, to be younger. 

Later, Dr. Houghton '' said he could not speak definitely as to the 
contemporaneousness" of this sandstone with that of Connecticut and 
New Jersey, " but he was sure of the similarity of their structure." % 
Prof B. Silliman, Jr. at the same time stated that although he had 
found the copper and silver from this region '* fused into perfect union 
at their two surfaces," they were not alloyed. § 

Prof John Locke, in an article in 1841, || entitled "Observations 
made in the Years 1838, '39, ^40, '41, '42, and '43 to determine the Mag- 
netical Dip and the Intensity of Maguetical Force, in several Parts of the 

* Am. Jour. Sci., 1841, (1,) XLT. 183-18G; 1844. XLVII. 106, 
Assoc, of Am. Cool, aivl Nat., 1840-1842, pp. 35-38. 
t Am. Jour. Sd., 1843, (1,) XLV. IGO. 

X Am. Jour. Sci., 1843, (1,) XLV. 332 ; 1844, XbVlI. 107, 132. 
§ Am, Jour. Sci., 1843, {!,) XLV. 332. 
11 Trana. Am. Phil. Soc, Phila., IX. 2S3-315, Apr. 19, 1844. 

Trans, of the 






United States," presents the metamorphic theory of the origin of the 
rocks of Keweenaw Point as follows: "The rocks of Copper Harbour, 
and indeed of the whole Kewenon peninsula, are decidedly metamor- 
phic, showing every degree of change produced by igneous agency, from 
unchanged sandstone to compact greenstone. The stratification is, 
mostly, more or less evident, presenting in the various superimposed 
layers, an inexplicable variety, some layers bearing evidence of 8cuii- 
fusion and a correspondent degree of induration and endurance, while 
others seem scarcely to have been altered, still remaining soft and yield- 
ing readily to atmospheric 'agency, and especially to the assaults of the 
■waves from the lake. Whether these differences have been produced 
by an nnecpial distribution of the heat, or by an original difference in 
the layers of the strata, some being of a nature more susceptible of 

change by heat, I was unable to determine Copi)er Harbour 

itself seems to have been formed by the removal of a softer stratum 
of metamorphic sand rock, while Porter's Island is a part of the barrier 
formed by the outcropping of a harder layer." {L c, pp. 311, 312.) 

In 1845,* Lieut. D. Rugglcs published a communication in which 
he advanced the view that the trap was projected in dikes through the 
New Red Sandstone, and that the veins were formed and fdled " by vol- 
canic or igneous action, under the pressure of incumbent waters." If 
■we can judge from his statements about the copper and his description 
of the filling of the veins in the "Lead Region " of Illinois, Wisconsin, 
and Iowa, he believed that these veins were filled by the projection of 
metallic copper, enveloped in a dense atmosphere of oxygen "from the 
fountain of igneous action, through fissures in the rock strata, resulting 
from concurrent disturbing causes." When the vein was "under the 
pressure of an immense mass of water," the oxygen entered into com- 
bination with the copper to form the black oxide of copper, but when 
only under atmospheric pressure the oxygen escaped by sublimation, 
leaving the copper to its own resources. 

Dr. Chas, T. Jackson, writing in 1845,t regarded the sandstones as 
probably Permian or New Red, but attributed to Dr. Houghton the 
belief that the formation is Old Red, and also held that the trappean 
rocks were injected dikes. The veins were taken as veins of igneous 
injection, although doubt is expressed, and he says : " When these veins 
occur near the trap dykes, analcime and Prelmite also abound, and were 
formed, without doubt, through the igneous agency of the trap on the 
contents of the vein and the ingredients of the wall rock." AVe may 

* Am. Jour. Sci., (1,) XLIX. 62-72. 

t Ibid., pp. 81-93. 



infer from tins, that he regarded the fissures to be of anterior formation 
to the traps. Tie states that " the trap rocks of Lake Superior pass 
through the red sandstone and conglomerate rocks, and are interfused 
with them, producing at or near their junction a very porous amygda- 
loid, which is always found at the lower side of the dyke where it is 
next to the sandstone." He also remarks that he fuids the copper and 
silver " united together side by side by fusion without any alloying of 
the silver " ; " the two metals are completely soldered together at their 
points of contact." This paper was also presented to the Association 
of American Geologists and Naturalists, at their sixth meeting, April 
184:5, published in their Proceedings (pp. 53- 60), and discussed by 
Prof. C. U. Shcpard (pp. GO, 61). He considered that the copper 
was derived from the sandstones by the action of the trap dikes upon 
them. The copper was originally in the" primitive rocks, " whose lateral 
slopes were occupied with cupreous strata derived from the degradation 
of the surrounding primitive ; and that whenever the trap had slid out 
beneath these deposits, or in other ways come in contact with them, 
they would, as elsewhere, bring to the surface rich masses of copper ; 
but he was inclined to the opinion that they would not give rise to deep 
and permanent mines." He considered that the sandstones belonged to 
the New Red. In an earlier portion of the Proceedings (pp. 30, 31), Dr. 
Jackson remarked that " at the junction of the great dykes with the 
sandstones of Nova Scotia, Maine, and on Lake Superior, a more violent 
ebullition took place than that which accompanied the eruption of the 
trap ranges in Connecticut, for the sandstone and trap are blown into a 
perfect scoria at the former localities ; amygdaloid resembling the most 
porous lavas, and immense quantities of trap tuff containing lumps of 
metallic copper, evince the powerful action of trap on the sandstones 
of Nova Scotia, and on Kewenaw Point, Lake Superior. .... On 
Kewenaw Point we have an intimate mixture of copper and trap rock 
in the amygdaloid, and I at first supposed if the amygdaloid resulted 
from the interfusion of sandstone and trap, that the copper might have 
been reduced from copper ores pre-existent in the sandstones ; but the 
absence of such ores in the sandstone in contact with or near the trap 
appears to discountenance the idea, and I am more disposed, since I 
have explored that region, to coincide with the opinion of Dr. Houghton 
in the belief that the copper of that region is a part of the primary 
copper of the globe brought up by the viscid trap." At a meeting of 
the Boston Society of Natural History,* November 6, 1844, he re- 

VOL. VII. — NO. 1. 

* Proceedings, I. 203, 





marked : " There can be no doubt, however, that the metals found in 
the Lake Superior amygdaloidal trap, have been fused at as high a 
temperature as was required to liquify the rocks in which they are 
found, for they bear evident marks of entire fusion, and are as vesicular 
as the common lavas of Vesuvius, Etna, and Peak of Teneritfe." * In 
one of the later paperst he states : " It is obvious, both from the crys- 
talline forms and the mode of occurrence of this copper, that it was 
deposited from a state of igneous fluidity ; and, from the circumstance 
that the walls of the vein are encrusted with Launionitc, it would 
appear that the spar vein itself is of igneous origin. Many other in- 
stances of a similar kind indicate that the calcareous spar veins, which 
traverse the conglomerate ^nd sandstone rocks, are true veins of igneous 







Mr. Bela Hubbard J regarded the sandstones on both sides of Kewee- 
naw Point as Potsdam in age, and held that the traps were eruptive in 
it. He regarded, however, the conglomerate and the "mixed conglom- 

erate and sand rock " lying to the northwest of the Point as of later 
origin than the trap and composed of itadebris. Concerning the *' mixed 
conglomerate and sandrock" he states: "As the finer strata of this 
rock have been mistaken by some for the red sandrock, hereafter de- 
scribed, it is important to observe that a very marked difference exists 
between the two rocks; for, while the latter is made up of materials 
derived from the several rock formations of the country, and into which 
quartzose grains enter most largely, the former is wholly derived from 
the trap rocks." The "red sandrock*' is said to be in nearly horizon- 
tal strata, but having on the coast a slight dip inland, which becomes 
"more apparent as it approaches the bayin of Portage Lake. In its 
approach to the trap, however, it is found more or less tilted from its 
original horizontal position, and is also very much altered by its contact 
with that igneous rock. The evidences both of the deposition of this 
extensive formation, in calm and shallow waters, and of the subsequent 
changes induced in it by the trap rocks, when in a fused or heated state, 
are very apparent." 

Prof. H. D. llogersj stated that "at the Eagle River mine, and 

* See also Proceedings of same Society, U. 110-114, Mar. 4, 1846. Am. Jour. 
Sci., (2,) IL 118, 119. 

t Proc. Best. Soc. Nat. Hist., 1846, U. 112. 

} Mineral Region of I/ike Superior, by J. Hongliton, Jr. nnd T. W. P>nstoL See 
also Senate Documents, 1849-50, 31st Cong., 1st Sess., III. 802-842, and 1845- 
46, 29th Cong., 1st Sess., VII., No. 357, pp, 2-29, 

§ Proc. Bost Soc. Nat. Hist., April 1, 1846, II. 124, 125. 



\ i 

: ll 

elsewhere, the metalliferous rock is not, as sonictimcs supposed, a real 
trap rock, but a mixture of trappcan matter, and that of the red sand- 
stone formation, more or less baked and modified by intense igneous 
action. These semi-fused materials, in crystallizing, have very fre- 
quently resulted in the following curious arrangement : the crystalline 
metallic copper occupies the centre of globular and variously, formed 
concretions; calcareous spar usually, but not always, invests the cop- 
per; and very generally the exterior of the kernel is pure crystalline 

chlorite These nodular lumps are dispersed through a base 

which exhibits a sort of pasty mixture of softened red shale and true trap- 
pean matter ; and many of them are so surrounded as to indicate them 
to be true segregations from this semi-igneous, semi-aqueous compound." 
He regarded the sandstone as equivalent to the New lied sandstone of 
the Atlantic States, and making the same formation throughout the 
peninsula of Upper Michigan. In a report on the sale pf mineral 
lands by Mr. Relfe we find the following statement: "In the con- 
glomerate rocks which overlay the trap, arc to be found all the varie- 
ties of copper ore of the richest qualities, ofTcring to the smelter a 
greater yield than ' has ever been obtained from the copper ores of 
England or other countries that have contributed so largely of this 

important article." * 

Sir Wm. Logan in the Report of Progrcsst regarded the copper-bear^ 
ing traps of Lake Superior as of a higher antiquity than the Potsdam 
Sandstone, and attributes the same view to Dr. Houghton in 1841. 
Logan's statement seems to be erroneous regarding Dr. Houghton's 
views in this respect. He considered the traps older than rocks which 
Logan regards as Potsdam sandstone, but of whose age he expressed no 
opinion in his Report for 1841, to which Logan refers. In 1843, as 
we have seen before, Dr. Houghton not only took the copper-bearing 
rocks to be of the age of the Now Red sandstone, but also considered 
Logan's Potsdam sandstone as belonging to some formation older than 
the Troutom In this way he had reversed his view of the order of 
succession in 1843, which Logan attributed to him as late as 1847. 

(L c, p. U.)t 

Mr. Bcla Ilvibbard in his report for 184G§ states concerning the trap 

* Kcporta of Comaiiiices, 29Lh Cong., 1st Scss., Vol. HI., Doc. 591, pp. 2,3, 

1845-46. • 

t Gcol. of Canada, 1846-47. 

t 1849 and 1851, Reports of Progress. Nortli Shore of Lake Huron, p. 20 ; Brit. 

AsHoe., pp. 59-62, 1851. 

§ Senate Documents, 1849-50, III. 371-935, p. 887. 



of the Porcupine ranges that, " while we desire to avoid any theoretical 
conclusions as to the mode of their formation, we cannot but observe 
that the character of the entire trap formation is rather that of a succes- 
sion of overflows, than of simultajieous uplift in mass ; in other words, 
it may be considered as made up of hech of the different kinds superim- 
posed upon each other." He also regards the " epidote veins " as in the 
main contemporaneous beds whose mineral contents were deposited 

with the bed. 

Dr. D. D. Owen, in his Ecport of a Geological Reconnoissance of the 
Chippewa Land District of Wisconsin, etc.,* of the date of April 23d, 
1848, regarded the sandstone of Lake Superior as younger than the Car- 
boniferous age, basing his conclusions, as Dr. C. T. Jackson had done, 
on lithological and mineralugical characters only. {l. c, pp. 57, 58.) 
In his final report (Oct. 30th, 1851, pp. 187-193), this view was aban- 
doned, and the sandstone regarded as Potsdam. 

Dr. C. T. Jackson t remarked in 1848 that the sandstone agreed in 
its characters with those of the oldest of the sandstone formations. On 
Jan. 2d, 1850, (l. c, p. 228,) he stated that he wished to correct the 
record, as the preceding view of the age of the sandstone should be 
accredited to his assistants, Messrs. Foster and Hill, and not to himself. 

Mr. James T. Ilodge -t seems to regard the veins as filled by igneous 
injection and sublimation. The silver was injected after the copper 
had cooled and occupied the spaces left by the contraction of the latter 

on cooling. 

Dr. Charles T. Jackson in his report (pp. 302, 398, 399, 471-473),§ 
transmitted November 10th, 1849, stated that the amygdaloid was 
formed by*' the interfusion of the rod sandstone and trap," and the 
trap rocks are distinctly stated to have burst through and between the 
strata of the pre-existing sandstone. He calls attention to the mooted 
question whether the trap rocks originated from the molten interior of 
the earth, or were derived from the re-fusion of'the lower stratified rocks 
(p. 397). The sandstone and conglomerate are said to have been de- 
rived from granite, gneiss, or mica slate and porphyry. The porphyry 
is thought to have resulted " from the semifusion of the finer materials 
of the sandstone. It' is evident at once, from inspection of the pebbles 

* Senate Documents, Ist Sess., 30th Cong., 1847-48, VIL, Doc. 57, 134 pp. 

t Pi-oc. Bost. Soc. Nat. Hist., HI. 76, 77, Nov., 1848. 

t Proc. Am. Ashoc. Adv. Sei., Aug. 20th, 1849, II. 301-308. 

§ Senate Documents, 1849-50, HI. 371-935. See also Proc. Am. Ass. Adv. Sci., 
H., 1849, Aug. 20, pp. 233-301 ; Bulk Geol. Soc. France, (2,) V(d. VII., 1849-50, 
pp. 667-673, and Am. Jour. Sci., (2,) Vol. X., 1850, pp. 65-77. 












\ - 




of the conglomerate, that they have been ground into their present 
shape by long attrition under wiitcr, or upon some ancient shore. 
.... They originated from some nether rock, or were transported 
to their present kcation by drift agencies." Dr. Jackson will then 
stand next iu order of time to Rev. J. G. Gumming in suggesting the 
idea of drift agencies in the earlier geological periods.* May wo sug- 
gest that these conglomerates are the lateral moraines of the ancient 
glaciers which scooped out the basin of Lake Superior, and that the 
coldness of the waters at the time of the melting of these glaciers pre- 
vented the existence of hfe then. In this way we account for the Lake 
basin, the conglomerates, and the absence of fossils, three difficult prob- 
lems. As we now know the geological structure of the country to be dif- 
ferent from that supposed by Dr. Jackson, there exists an excellent field 
here for speculation concerning the number of glacial periods during 
the time of the deposition of the rocks of Keweenaw Point, the con- 
nection of glaciers with volcanic action and the eccentricity of the 
earth's orbit. It is very probable that the ice by its weight carried the 
sedimentary strata downwards, the same pressure aiding in their igneo- 
aqucous fusion (solution), while the thickness of the ice mass would 
cause the gcothermal couches to rise, thus enabling us to account for 
the lavas. This leads us to the consideration of the ofToct that glaciers 
may have in forming lake bottoms by their pressure bending the under- 
lying strata, the displaced material being erupted along the sides of the 
depression. We can thus account for the proximity of volcanoes to 
large bodies of water, and explain the cause of the highest mountains 
being adjacent to the deepest oceans, their successive elevations cor- 
responding to the different glacial epochs. If the Atlantic is to be 
filled with a solid mass of ice to account for the loess of the Rhine, and 
the Southern oceans to be filled in like manner to explain the geographi- 
cal distribution of the New Zealand faima, why cannot Lake Superior 
also be filled, wlien it will cost so little and explain so much'? 

Dr. Jackson further considers the sandstone as belonging to the New 
Red, stating that it has been absolutely proved not to be Potsdam. He 
seems to have receded from his former views regarding the filling of the 
fissures by vein material and not to have adopted any others in their 
places, lie would, however, consider that the copper and silver *' were 
produced by igneous agency The copper and silver occur on 

* History of the Isle of Man, 1848, p. 89. So^i also F. B. irough, Proc. Am. 
Assoc. Adv. Sci., 1851, VL 262-264 ; and the Quart. Jour. Geol. Soc, VI. 96, 97, 
1850, K Godwin Austin ; XI. 185-205, 1855, A. C. Ramsay. 



Lake Superior mineral lands in the trap rocks only, and the valuable 
veins are limited to a narrow belt of the amygdaloidal variety of that 
rock." {I c, p. 471.) Mr. J. W. Foster (May 26, 1849, /. c, i)p. 773- 
785) regarded the sandstone " as resting at the base of all the fossil- 
iferous rocks." 

In Foster and Whitney's Report to the Laiad-Ofiice {I. c, p. G07), it 
is stated that " what is generally known as the trap range, consists of a 
belt of igneous rocks, composed for the most part of hornblende and 
felspar, which in places have broken through the sandstones, tilting them 
np at high angles ; but oftener are found in alternating beds, having 
the same dip as the detrital rocks. The associated sandstone and con- 
glomerate belong to the silurian system, and rest at the base of all 
fossiliferous rocks." Concerning the copper it is stated : "Some of these 
accumulations of copper are mere beds, the result of segregation, while 
others are contained in fissures, formed subsequent to the containing 
rock, and associated with a veinstone entirely dissimilar." (I. c, p. 608.) 

The final report of Messrs. Foster and Whitney on the Copper Lands 
was presented April 15, 1850.* Regarding the trap range of Keweenaw 
Point, it is stated that " this range does not appear to have been the re- 
sult of one, but of successive overflows ; for we not only find the igneous 
materials arranged in parallel bands, and exhibiting great diversity in 
external characters, but we also find numerous intercalations of con- 
glomerate of inconsiderable thickness, but extending for miles in a linear 
direction — these mixed products being associated in regular beds, having 
a common bearing and inclination, so that the inexperienced observer is 
inclined to refer the whole to a common origin. This deception is still 
further increased by observing lines of pseudo stratification in the trap 
conforming to those of the associated sedimentary rocks." {l. c, p. 61.) 

The southern trap range of the Point is said to consist of "a vast 
crystalline ma^s, forming an anticlinal axis, flanked on the north by the 
bedded trap and conglomerate, and on the south by conglomerate and 
sandstone." {L c, p. 64.) Towards Portage Lake none of this trap 
was protruded, but it was thought that the same fissure extended along 
this line from the ''head of Keweenaw Point to the western limits of 
the district." (/. c, p. 68.) Regarding the relations of the sandstoTie to 
the trap on Keweenaw Point and Isle Royale, they say : '* As a general 
observation, the upjier portions of these sandstone belts are much 
more changed by heat than the lower." {L c, p. 63.) "The upper por- 
tions of the sheets of trap are highly vesicular, resembling pumice. 

* Executive Documents, 1st Scss,, 31st Cong., 1819-50, IX., Doc. 69, 224 pp. 




< - 











4 + 



Fragments of amygdaloid, sometimes rounded, at others angular, aro 
found enclosed in the pumice-like trap, as though tliey had become 
detached and afterwards reunited to the mass, while in a molten state. 
Numerous short and Irregular fissures, extending to no great depth, aro 
observed on the upper surface of the trap, in which sandstone has been 
deposited Between the sandstone above and the trap heloiVj it is ex- 
tremely difficult to determine where the one begins, and the other ends. 
Fragments of amygdaloid, angular or partly rounded, are included 
in the sandstone — more numerous near the base than at the top of the 
deposits. Whei'c the sandstone is imposed 07i the trap, there is little 
evidence of its having been metamorphosed ; but, on the other hand, 
■where the trap rests on the sandstone, the line of junction is clear and 
well delined. The trap is less vesicular; and the upper portion of the 
sandstone belt, for the distance of three or four feet, is converted into a 
ribbon jasper, having a compact texture. These phenomena have been 
observed at numerous places both on Isle Eoyale and Keweenaw Point. 
The beds of sandstone are not shattered, nor docs the igneous rock pene- 
trate in the form of dikes or ramifying veins. All the phenomena indicate 
that the igneous rocks were not ]3rotruded in the form of dikes between 
the strata, but that they flowed like lava sheets over the pre-existing 
surface ; and that the sand was deposited in the fissures and depressiona 
of the igneous belt, in some cases while the mass was in an incandescent 
state." {I. c, p. 87.) The conglomerate is regarded as a volcanic tuff, 
and the sandstone as Potsdam in age. The conglomerate of Keweenaw 
Point and Isle Royalo " consists of rounded pebbles of trap, almost in- 
variably of the variety known as amygdaloid, derived probably from the 
contemporaneous lavas, and rounded fragments of a jaspery rock which 
may have been a metamorphosed sandstone, the whole cemented by a 
dark-red iron sand. This cement may be regarded as a mixture of vol- 
canic ash and arenaceous particles, the latter having been derived from 

the sandstone then in the progress of accumulation The trap- 

pean pebbles often attain a magnitude of eighteen inches in diameter. 
Tlieir surfaces do not present that smooth, polished appearance which 

results from the attrition of water The conglomerate appears 

to have been formed too rapidly to suppose that the masses were 
detached and rounded by the action of waves and currents, and 
deposited with silt and sand on the floor of the ancient ocean ; for, 
while the contemporaneous sandstone remote from the line of volcaulo 
foci does not exceed three hundr(^d or four hundred feet in thickness, 
the united thickness of the conglomerate bands in the vicinity of the 






" Although the conglomerate 

trappean range on Keweenaw Point exceeds five thousand feet. As we 
recede for a few miles from the line of the volcanic fissure, these amyg- 
daloid pebbles disappear, ^nd are replaced by arenaceous and argil- 
laceous particles." {I. c, pp, 99, 100.) 
attains a thickness of five thousand feet, yet it by no means follows that 
the ancient sea in which it was deposited extended to that depth. Ripple- 
marks and clay-cracks have been observed in the upper portions of this 
group ; the one indicates comparatively shoal water, and the other the 
ebbing and flowing of a tide, or a change in the level of the water. The 
inference, therefore, is, that during the deposition of the conglomerate, 
the bed of the sea was subject to repeated elevations and depressions, 
caused by volcanic action, and that its water obeyed the same tidal laws 
which govern the existing oceans. These conglomerates, then, may be 
regarded as local deposites formed along the courses of the volcanic 
fissures by the joint agency of fire and water. When the former causes 
operated with intensity, the materials consisted of spherical masses of 

When they acted feebly, or were quiescent, the ma- 

" We have 

lava and scoriae. 

terials became argillaceous or arenaceous." (/. o., p. 109.) 

seen that, during the deposition of the sandstone, numerous sheets of 

trap were ejected, and flowed like lava-streams ; and that the igneous 

and aqueous products were so intermingled as to present the appearance 

of having been derived from, a common origin ; and that subsequently 

the unbedded trap broke through these parallel fissures, lifting up the 

sandstones, conglomerates, and bedded traps, and causing the whole 

mass to dip at high angles.'* {I c, p. HO.) The sandstone on both 

sides of Keweenaw Point, and the trap, were regarded as making one 

geological formation. 

While the sandstone is stated to dip near the southern range of trap 
above B(;te Griae Bay 78*" southeast {l. c, p. 112), farther up Keweenaw 
Bay the prevailing dip was said to be about 5° to the northwest (/. c, 
p. 116). The veins were regarded as probably filled by materials *'once 
held in aqueous solution and precipitated by electro-chemical agency," 
while the theories of sublimation and injection were controverted (/. c, 
pp. 174, 175). The veins were fully described so far as then known, as 
well as the order of deposition of the minerals and associated copper, 

Prof. Louis Agassiz, in discussing the " Geological Relations of the 


* See also Bull. Gcol. Soc. France, (2,) VII. 1850-51, pp. 89-100 ; Proc. Am. 
Assoc. Adv. Sci., 1851, V. 22-38, 136-151 ; aud Am. Jour. Sci., (2,) 1851, XII. 
222 - 239. 


-tH i-'o— X ^ tr^j--=TJi-" 

n KJTiiiE+iWCKcTr^-^-T y F^i ?>^^ 




various Copper Deposits of Lake Superior," * wrote concerning the copper 
ores : ** They seem to me clearly to indicate that the native copper is 
all plutonic ; that its larger masses were thrown up in a melted state; 
and that from the main fissure through which they have found tlieit 
way, they spread in smaller injections to considerable distances; but 
upon the larger masses in the central focus, the surrounding rocks 
could have little influence. New chemical combinations could hardly 
be formed between so compact masses, presenting, in comparison with 
their bulk, a small surface for contact with other miuci'al substances 
capable of being chemically combined with the co[)per. But where, 
.at a distance, the mass was diffused in smaller proportions into innumer- 
able minute fissures, and thus presented a comparatively large surface 
of contact with the surrounding rocks, there the most diversified com- 
binations could be formed, and thus the various ores appear in this char- 
acteristic distribution. The relations which these ores bear to the rocks 
in which they are contained, sustain fully this view, and even the cir- 
cumstance that the black oxide is found in the vicinity of the mam 
masses, when the sulphurets and carbonates occur at greater distances 
from them, would show that this ore is the iTsuIt of the oxidation of 
some portion of the large metallic masses exposed more directly to the 
influence of oxygen in the process of cooling. Indeed, the phenomena 
respecting the distribution of the copper about Lake Superior, in all 
their natural relations, answer so fully to this view, that the whole pro- 
cess might easily be reproduced artificially on a small scale ; and it ap- 
pears strange to me that so many doubts can still be expressed respecting 
the origin of the copper about Lake Superior, and that this great feature 
of the distribution of its various ores should have been so totally over- 

Prof. J. D. Dana remarked : " The copper occurs in trap or sandstone, 
near the junction of these two rocks, and has probably been produced 
through the reduction of copper ores by the heat of the trap when first 
thrown up." f This view is retained in his later editions of the same 
M- o rl^ . t 

Dr. C. T. Jackson later advocated his former view that the sandstone 
of Keweenaw Toint was of the same age as the New Red sandstone of 
Europe, but in addition he claimed that this sandstone (New Eed) was 

*■ Lake Supciior : its Physical Character, Vegetation, 
March, 1850,) pj). 427, ^28. 

t Syatcm of Mineralogy, 3d ed., May, 1850, p. 508. 
t 4th ed,, 1854, Part II. p. 17 ; 6th ed., 1868, p. 15. 

and Animals, ( Boston, 



a member of the Upper Silurian * Later, Mr. Jules Marcou advocated 
the view that this sandstone was of the age of the New Red, and opposed 
the ideas of Messrs. Foster and Whitney.f At the meeting of the Brit- 
ish Associati<Hi for the Advancement of Science, July, 1851, Sir W. E. 
Lo-an t advanced the idea that the sandstone and its associated traps 
were older than the Potsdam, and of Cambrian age. This Yiew was 
based on the idea that the azoic rocks north of Lake Huron were the same 
as the traps of Keweenaw Point.§ Dr. D. D. Owen, as mentioned before, 
in his " Geological Survey of Wisconsin, Iowa, and Minnesota" (pp. 18 <- 
19G) ro<rardcd the sandstone as of the same age as the Potsdam of Wis- 
consin, \ut Col. Chas. Whittlesey (Ibid., pp. 459-4G1) was inclined 
to think it was older. Dr. J. J. Bigsby|| believed the sandstone to be 
Cambrian (or Silurian). Later, Dr. C. T. Jackson advocated tlie igneous 
origin of the calcite veins in this region. H Mr. Jules Marcou, m his 
" Geological Map of the United States, with Text," held that the sand- 
stone was of the age of the New Red, and apparently regards the trap as 
having been injected in the form of dikes. The copper veins were also 
thought to be dikes, with the copper of like igneous origin. This work 
gave rise to a long controversy, in wliich the age of the sandstone was 
quite thoroughly discussed ; but in only a few cases shall we refer to the 
various articles elicited by it. Those interested in the literature of the 
Marcou - Anon.- Agassiz - Barrande - Blake - Dana - Hall -Hunt - Logan - Mur- 
chison-Whitney controversy will find the principal articles, that have 
any bearing on the geology of Lake Superior, given under the names of 
the different authors in the list of articles at the end of this paper. 

The same views regarding this district that were given in Messrs. 
Foster and Whitney's Report on the Copper Lands were again pre- 
sented in brief in Professor Whitney's " Metallic Wealth of the United 
States " * * Dec. 5th, 1855, Dr. Jackson explained the deposition of 
the copper in the veins " as the result of the chemical action of 
protoxide of iron in the trap-rook, which decomposed the vapor of 
chloride of copper, as it rushed from the interior of the earth tlirough 
the crevices ; if, as is probable, these wonderful native copper lodes, are 

* Proc P,ost. Soc. Nat. Hist., Oct. 2 and 16, 18.50, 111. 335-339. Sco also Bull. 
Soc Geol. France, (2,) 1849-50, VII. 209, Elie de Beaumont, 
t Bull. Soc. GeoL France, 1850-51, (2,) Vlll. 101 -lOo. 
} Trans, of the Sections, pp. 59 - 62. 
§ See Am. .Tour. Sci., (2,) 1857, XXIII. 305-314. 
II Edmburgh New PUil. Jour., 1852, bill. 55-62. 
t Proc. Bo°t, Soc. Nat. Hist,, 1853, IV. 308, 309. 
« Pluladelpliia, 1854, pp. 247-305. Am. Jour. Sci., (2,) 1857, XXIII. 30o-314. 

— ^-j I -J— -+::l^^- ^^>:ti 

I . ^r^ r^ LLKi^-^Z.^ A"^ 



the products of sublimation and of galvanfc segregation of the metal 
from vapor." He defined the ash bed as a " comparatively soft scoria, or 
rotten amygdaloid, formed by the mixture of molten trap-rock and fine 
sandstone, which have been, as it were, melted together into a very 
spongy kind of scoria, the aqueous vapor having rendered it remarkably 
vesicular."* He regarded the trap as having been "poured out, at dif- 
ferent times, through a fissure, and spread over the materials of the 
sandstone and conglomerate at the bottom of the sea, thus producing 
alternating beds of these rocks," while in July, 1856, he seems to have 
regarded the trap as forming dikes in the sandstone, and combining with 
its ingredients to form the zeolites.f Prof. L E. Kivot t regarded the 
traps as interstratified sedimentary beds metamorphosed in situ. The 
sandstone formed the upper portion of, and was conformable with, 
the copper scries ; all to the Sault St. Marie making one geological 
horizon, including the granites and iron-bearing rocks. All were taken 

to be of the Potsdam age. The veins were considered to have been pro- 
duced by elevation and fracture since the deposition of the entire scries, 
and tlie copper deposited in the wet way. 

In 18,?6 a " Report on the Exploration of Lakes Superior and Huron," 
was presented to the Legislative Assembly of Canada by Count de 
Eottermund. It probably proved satisfactory, as we do not learn that 
the Assembly asked for any further information from him. Li the nar- 
rative portion we are informed : "I procm-ed a boat with four hands 
and proceeded to Portlock Harbour. ... I met Mr. Salter with whom 
I returned to the Bruce Mines. There we parted our provisions and 
separated." {L c, p. L) 

He attempts a classification of the formations visited, and states that 
" this classification demands great attention, and very minute discrimi- 
nation, to avoid the solecism of giving names according to individual 
fancy, not used in the scientific world. Such are the names applied to 
formations m Canada of Huronian, Sillery, Laurentine, Pichclicu, pecu- 
liar to tiie localities which they indicate, substituted for Jurassic, Car- 
boniferous, Cambrian, Devonian, etc., which arc so well classified, defined, 
and admitted throughout the scientific world." {I c, pp. 4,5.) 

His theory of tiie origin of the copper is too lengthy for'inscrtion ; it 
nnist be read to bo appreciated. The result is summed up as follows : 
''On Lake Superior the copper, in its native state is due to the de- 

* Proc. Bost. Soc. ^^at. Hist., 1855, V. 279-281; 1850 VII 31 
t Ibid., VI. 23, 24. 

\ Auiialos dcs Minos, (5,) 1855, VII. 173-328 j^lSSG, X. 364-474. 





l^osit of certain species of organic matters whicli have a tendency to 
increase the electro-chemical action, and which decomposed the sulphu- 
rets, oxides, etc., which tlie abundant deposit of matter containing traces 
of talc serpentine and chlorites, has brought together or concentrated 
in a certain limited space. For nearly all the rocks contain in the 
crystalline cleavage, and also in the veins these matters which appear 
sometimes to be a sort of cementation, if, indeed, it be not the state 
of combination of detritus, of disintegration of primitive rocks which 
have arrived at the state of sandstone and groywacke.'' {I. c, p. 13.) 

This report is not without interest to the archjcologist as the follow- 
ing proves : '^ I have in my possession locks of hair enveloped in copper, 
which tlio natives carried about them as marks of their bravery. When- 
ever they killed their enemy they used to cut off a lock of hair and carry 
it about them as a species of decoration. In places where there is no 
copper they cut off with tlie hair a small portion of the skin, which is 

called the scalp." (/. c, p. 16.) 

The student of Indian customs can, of course, now greatly aid the 
miner in his prospecting, if he will carefully map the districts inhabited 
by the non-scalping, copper-bearing Indians, for hereafter it will be of 
no avail to look for copper outside of their habitat. 

Alb. Muller, in 1856, published a paper relating to the copper of this 
district.* Ilis facts were taken mostly from the report of Foster and 
Whitney, and it is unnecessary to repeat them here. Ho regarded the 
copper as being deposited in the wet way, by the aid of galvanism, and 
reduced by organic matter and the oxide of iron. The copper, it is sup- 
posed, might have existed in the trap and its minerals, in minute 
amomits, until brought to the points where it is now found. The stu- 
dent interested in the origin and deposition of the copper will do well 
to read the writings of Foster and Whitney, AVhitney, Muller, Baucrman, 
and, lastly, those of Marvine and Pumpelly. 

PrincipalJ. W. Dawson remarks t concerning the deposition of the 
native copper: "The whole of the appearances indicate that tlie depo- 
sition of copper belongs to the period of aciueous infiltration, by which 
the veins and vesicles were filled after the consolidation of the trap ; 
and the copper, like the calc sjiar and zeolites, occurs both in true veins 
and in the cavities of beds of vesicular trap and tufa. Its deposition 
must, therefore, be explained, not by igneous causes, but by clectro- 

* Yorhandlungen dcT ■Naturforscliciidcn Gcsellsdiart in Baiicl, 1854-57, pp. 


t Feb. 10, 1857. Canadian Nat. and Geol., II. 1-12, 



clioniical agencies, decomposing some soluble salt, most probably the 
sulphate, of copper. Such changes may have been aided by the remain- 
ing heat of portions of the volcanic masses, by the proscnco in them of 
large quantities of iron in low states of oxidation, and by the further 
oxidation of that metal evidenced in the red jasper and red laumonite 
of the veins, and the red conglomerate and sandstone associated with 
the trap The main fixct in relation to the origin of the metallic cop- 
per, is that it is a product, not of the fusion of the trap, but of subse- 
quent processes, by which the fissures of that rock were iillcd by mate- 
rials regarded as of aqueous origin." (/. c, pp. 8, 9.) 

In 1857, Dr. J. D. Dana'^ stated that the veins occur ''mostly in the 
trap rock which intersects a red sandstone, probably identical in a<^e 
witli the red sandstone of Connecticut and New Jersey." April 6, 1859, 
Dr. Jackson inclined to the view that the zeolites had been formed 
"under the heat of the trap rocks, and the inilucuce of heated saline 
waters." t Prof. James Hall, in his Palioontology of New York, J says : 
"In the region of Lake Superior, the sandstone, of the age of the Pots- 
dam sandstone, has accumulated to a degree unparalleled in any other 
known locality of that rock. In this I'cgion there arc not onlj^ massive 
accumulations of trappean mattei", but outflows which have spread over 
the strata during tlieir deposition ; the beds of stratified amygdaloid 
trap alternating with tlie shale and sandstone, uften equalling or exceed- 
ing the sedimentary matter." 

In 1861, Dr. T. Sterry Hunt, following Logan, referred the sandstone 
with its accompanying trap to the Quebec gi'oup.§ Prior to this,|| Prof. 
W. B. Rogers supported the view that this sandstone was of Potsdam 
ago, and was opposed in this by Dr. Jackson. 

In his Manual of Geology,1[ Dr. Dana refers the sandstone partly to 
the Potsdanx and partly to the Calciforous cpocli. In the edition of 
1871, it is regarded as Calciforous. Dr. Dana further remarks concern- 
ing the copper, that ''the native copper of the Lal^:c Superior region is 
intimately connected in origin with the history of the trap and sandstone. 
The copper occurs in irregular veins in both of these roclis near their 
junction ; and whenever the trap was thrown out as a melted rock, the 

* Jhm. of AOu., 2.1 eil., p. 305. 

t Proc. r5ost. So(\ Xat. iliyt., 1359, Vll. 45-i7. 
I Vol. 111. p. 79, 1859. 

§ Am. Tour. S^n., {%) I8G1, XXXL 216-220, 392-414 ; 1862, XXXllI. 320- 
327. Ciuiadiuu Nat, and OooL, 1861, VI. 81-105, 199-207. 
Proo. Boyt. Sue. Nat. Iliat., Nov. 17, 1860, VII. 394-399. 
IT 1862, pp. 172-174. 




copper probably came up, having apparently been derived from copper- 
ores in some inferior Azoic rocks through which the. liquid trap passed 
on its way upward. The extent to which the rock and its cavities are 
penetrated and filled with copper shows that the metal must have been 
introduced by some process before the rock had cooled."* 

In the Geology of Canada, 18G3, the copper-bearing rocks are con- 
sidered, by Sir -W. K Logan, to be of the Calciferous and Potsdam 
formations, but overlaid by the Eastern sandstone, which was regarded 
as Chazy (pp. G7-86). Dr. Hunt seems to regard the "ash-bed" of 
Copper Falls as a conglomerate, and further says, regarding the Port- 
age Lake deposits : *' Certain of the sedimentary beds thus impregnated 
with native copper, are often designated as volcanic tufa or volcanic 
ash. From whatever source derived, however, the amygdaloidal rocks 
were deposited from water ; and the copper which is disseminated in 
them, as well as in the sandstones and conglomerates, was separated by 
chemical processes from aqueous solutions, either contemporaneously 
or by subsequent infiltration. There appears to be no doubt that the 
traps which are interstratificd with the sandstones and amygdaloids of 
this region, are eruptive rocks; and the sedimentary material of which 
the amygdaloids and tuf^is are composed may pcrhap.s have been, to a 
greater "^ or less extent, erupted in the form of volcanic mud, as many 
geologists suppose. This origin of the sediment has probably, however, 
no connection with the source of the copper.'* (pp. 698, G99.) He 
takes the entire formation, as before, to belong to the Quebec group. 

In 18GG, Mr. Thomas Macfarlane regarded the rocks at Portage Lake 
as melaphyrs.t In 18G8 (/. c, p. 25G), he appears to regard the sand- 
stone as being of the Permian ago, basing his conclusions upon the litho- 
logical characters of the melaphyrs, while those who had regarded it a> 
Trlassic have based their views upon the lithological characters of the 
sandstone. One method is about as valuable as the other, a flow of 
basalt lava or a deposit of saiul not being apt to be dated j^er se. Colonel 
Whittlesey, in describing the continuation of this formation in Wiscon- 
sin, makes the copper-bearing trap a formation below, but conformable 
with the Potsdam sandstone, t Mr. H. Baucrman§ suggests, besides the 
hypothesis of Muller, the folhnving to account for the occurrence of the 

* Kdition of 1862, ^i. 195 ; see also edition of 1874, p. 186. 

t Geology of Caiuulu, 1866, pp. 149-164. Canadian Nat. and Gool., (2,) HI. 


: Proc. Am. Assoc. Adv. Sci., 1867, XVI. 97-107. 

§ Quart. Jour. GeoL Soc, 1866, XIL 448-463. 



copper : '' The presence of copper in the sandstones suggests another 
origin — namely, that it may have originally been deposited with the 
quartz-ore sediment as a finely divided sulphide from sea-water under 
the influence of organic matter, and by subsequent oxidation and solu- 
tion have been removed and collected in the rocks below The size 

of the accumulated masses of metal appeal's to be mainly dependent 
upon the size of the cavities in which they are deposited, whether in 
the amygdaloids or in the main fissures ; and their absence in the com- 
pact traps is probably only due to the non-occurrence of such cavities. 
In almost all cases the introduction of the metal has been preceded 
by the deposit of minerals produced from the decomposition of the 
rock, such as quartz, calcite, cldorite, and zeolite ; and in the larger 
cavities it is often followed by transparent crystals of calcite, which are 
fonned over branching masses of copper, or even show signs of simulta- 
neous deposition, being filled wuth fire-spangles of metal arranged par- 
allel to the diagonal striations or lines of growth on the rhombohedra. 
Similar alternation>s in the formation of zeolites, more particularly 
analcime, have been described by Whitney." He is inclined to regard 
the deposition of the copper in the amygdaloids as having tidcen place 
prior to the filling of the veins, the former serving as feeders to the 
latter. (I. c, pp. 4G0, 4G1.) 

In a paper read before the Boston Society of Natural History, June 
5, 18G7,* Mr. Alexander Agassiz remarks: "Foster and Whitney, in 
their Report of the Lake Superior mineral district, represent the sand- 
stone on the south side of the trap range of Keweenaw Point as dip- 
ping south and resting conformably upon the beds of trap of the north 
side of the anticlinal axis of Keweenaw Point. Tliis anticlinal axis 
formed by the Bohemian Mountain, as asserted by Foster and Whit- 
ney, is not found further south as far as I have had occasion to examine. 
In two of the ravines cut through the sandstone by creeks flowing in 
an easterly direction from the crest of the range towards Torch River, 
near the head of Torch Lake, we find good exposures of the sandstone 
resting unconformably upon the trap which has still the same northern 
dip as farther west, of about 42°. The sandstone within a distance 
of one hundred feet from the trap, dipping nortli 42°, lies horizontally, 
or rather has at the outside an inclination of 1-|° or 2° south." At the 
falls of the Douglass Houghton Creek, he says : " The creek winds its 
way through a deep ravine cut out of the sandstone, and at the junction 
of the sandstone and trap, falls a depth of one hundred and sevcnty- 

* rroooedings, XI. 244 -2i7. 



On breaking 

two feet. The cliloritic bed is well developed on tbo soutli side of 
tbe creek, while the north side is more greenstone, and all along the 
whole length of the ravine np to the Mis, a distance of one and one- 
half miles, the horizontal beds of sandstone arc readily traced, dipping 
sjightly north near the falls, and being horizontal at the opening of tlie 
ravine into Torch Eiver valley, plainly showing that they rest uncon- 
formably upon the trap range. On examining this sandstone more 
carefully, we find that the strata are made up of alternating layers of 
sandstone of reddish or yellowish grain, and of beds of loose sandstone 
containing boulders ; some of the beds of boulders resembling what is 
common on sca-shorcs as a mixture of mud and shingle, 
open several of the small boulders taken in situ from the beds we find 
that they consist mostly of reddish trap, but frequently we come across 
perfectly well water-worn boulders of grayish trap containing amygdales, 
identical with the trap of the copper range a short distance west from 
these beds of sandstone, plainly showing that the sandstone was depos- 
ited upon the shores of the ridge of trap forming Keweenaw Point, and 
has not been uplifted by it as is stated by Foster and Whitney. The 
case is totally different with the sandstone north of the range that lies 
conformably upon the trap, but the sandstone of the southern side of 
the mineral range in the vicinity of Torch Lake is plainly of a different 
age, lying, as it does, unconformably upon the former." 

In some respects it would seem that Mr. Agasslz, in common with 
many geologists, had misunderstood the views of Messrs. Foster and 
Whitney. Their idea was that the traps and sandstone comprised the 
same formation. The present visible portion of the eastern sandstone 
had, like the western one, been laid down since the trappean overflows. 

After the deposition of the entire series a fissure was formed running 
along the Point from its head to the western limits of the district. 



was attended in the northeastern portion by the protrusion of trap 
forming the Bohemian Mountains, but towards Portage Lake the fissnr- 
ing was accompanied only by the elevation of the sandstone and trap 
west of the line, while that cast of it remained nearly horizontal. As no 
stratified rock can rest conformably on the intrusive mass which uplifts 
it, so the sandstone was not supposed to rest conformably on the Bohe- 
mian trap. They also did not in their final report regard the sandstone 
along this fissure at the Douglass Houghton fall as dipping southerly, 
although Mr. Foster had stated so in a previous report to Dr. Jackson.* 
That Messrs. Foster and Whitney had this idea was probably inferred 

« Senate Doc, 1849-50, III. 783. 



from the fact tliat the printer placed the eastern side of their section on 
the left hand, as was also done with that of the Copper Falls mine.* 
Their idea then would be perfectly consonant with the presence of 
trappean pebbles in the eastern sandstone as well as in the western, only 
they would have been deposited prior to the faulting, instead of after itj 
as Mr. Agassiz's view would demand. 

Mr. Robert Bellt regards the Upper Copper-bearing rocks as being of 
Permian or Triassic age. This conclusion was based on the lithologi- 
cal characters, and was objected to by Sir Wm. Logan in the same 

report (pp. 472-475). 

Prof K Pumpolly in 1871 published a paper on "The Paragene- 
sia and Derivation of Copper and its Associates on Lake Superior," J a 
subject which had been treated of before by Messrs. Whitney, Mullcr, 
and Bauennan. 

He remarks: ''The eastern limit of the 'range* 


formed by a strongly marked and generally vertical plane of demarka- 
tion between the highly inclined cupriferous series of rocks and the 
sandstones which slope gently to the S. E. This sudden break is con- 
sidered, with probably the best of reasons, by Foster and Whitney, and 
afterwards by Rivot, to be a longitudinal fracture accompanied by a dis- 
location of at least several thousand feet. Foster and Whitney looked 
upon the sandstone as the equivalent of the Potsdam, while the Geol- 
ogists of the Canadian Survey refer it to the Chazy, and both authorities 
agree in considering it to be younger than the cupriferous rock, and of 
the same age as the sandstone beds, which are conformably superim- 
posed over the trappean series on the west side of Keweenaw Point,'" 

Prof. Pumpelly, it would seem, believed that the copper was de- 
posited in the places in which it is now found by being precipitated 
from solution through the agency of protoxide of iron. He further 
considered that the copper was derived by concentration from the sedi- 
mentary members of tlic scries. He remarks that " it is still an open 
question whether the trap which formed the parent rock of the mela- 
phyr was an eruptive or a purely metamorphic rock. If it was erup- 
tive, it was spread over the bottom of the sea in beds of great regularity, 
and with intervals which were occupied by the deposition of the beds 
of conglomerate and sandstones." (/. c, p. 352.) The general tenor of 
this and his other papers shows that at this time, and for some years 
afterward, he leaned strongly towards the theory of the sedimentary 

* Copper LaiK^s, pp. 63, G8. 

t Geology of CEiimda, 1866-69, p. 321. 

t Am. Jour. Sci., (3,) H. 188-198, 243-258, 347-355. 

VOL. VII. — NO. 1. 7 

■ 4 




origin of the entire trappean series. At this time he also regarded 
the traps, with all the sandstone as far east as at least the Pictured 
Ptocks, as belonging to the Quebec group. It will be seen that he 
afterwards abandoned these views. 

Later, Prof Pumpelly in conjunction with Major T. B. Brooks pub- 
lished a paper entitled, " On the Age of the Copper-bearing Eocks of 
Lake Superior."* They state that their observations "demonstrate a 
wide difference in age between the Cupriferous series of sandstones, con- 
glomerates, and melaphyres on the one hand, and the Lower Silurian 
sandstone, with which they have generally been considered as nearly 
identical in age, on the other." At the western edge of the eastern 
sandstone on Keweenaw Point " its nearly .horozontal strata abut against 
the steep face of a wall formed by the upturned edge of beds of the 
Cupriferous series of melaphyre and conglomerate, which dip away from 
the sandstone at angles of 40° -60°, according to geographical position. 
This sharply defined and often nearly vertical plane of contact, having 
been seen by the earlier geologists at several points along a distance of 
many miles, and having been found to be often occupied by a thick bed 
of chloritic fluccan, which was looked upon as the product of faulting 
motion, was considered as a dislocation. This idea seemed to gain cor- 
roboration in the fact that, on the western side of Keweenaw Point, sand- 
stones bearing considerable resemblance to those of the eastern horizontal 
beds occur, apparently conformably overlying the Cupriferous series. 
Both sandstones came to be considered as identical in age, and as form- 
ing the upper member of the group. There were many circumstances 

■ r 

which made it difficult for us to accept this conclusion. One obstacle 
lay in the enormous amount of dislocation required ; for instance, at 
Portage Lake, where the strata of the Cupriferous series, with an actual 
thickness of several miles, dip away from the supposed longitudinal fault 
at an angle of about G0°." The Cupriferous scries is regard<.)d by them 
as conformable to the Iluronian, wliilc the line of fault is taken to bean 
old shore cliff, with the sandstone deposited against its base. They also 
state that it would be difficult to account for the absence of this series 
in localities eighteen miles from where they were found miles in thick- 
ness, unless they represented a sinking area along whose shores the Silu- 
rian sandstone was deposited. They also claim that this scries was worn 
through near Lake Gogebic, and the Silurian sandstone de[)osited in the 
trough. It is to be noticed that according to them the Cupriferous 
series are four miles distant from the locality in which the Silurian 

* Am. Jour. Sci., (3,) TIL 428-432, 1872. 





sandstone is said to have been seen. Their geological reasoning could 
only hold good in a region where uncontorted sedimentary rocks alone 
occur; therefore we are justified in believing that at this time both 
Pumpelly and Brooks regarded the copper-bearing traps as metamor- 
phosed sedimentary rocks. We are not aware that the latter has ever 
changed his views. 

In 1873, Dr. T. Sterry Hunt* used the term Keweenian group in 
speaking of the copper-bearing rocks, and suggests that perhaps the 
copper may have been derived from the oxidation of copper ores in the 
Huronian schists, while the dissolved metal accumulated in the basins 
at their base, — a view almost identical with that announced by Shepard 
twenty-eight years before. " We may here remark that the late re- 
Bearches of Messrs, Brooks and Pumpelly seem to establish that the 
great copper-bearing scries of Keweenaw occupies a place between the 
Huronian schists and the nearly horizontal i*ed and white sandstone of 
the region which is itself below the Trenton limestone. In all this they 
have confirmed the previous conclusions of Houghton, Whitney, Hall, 
and Logan." It may be remarked here, also, that if Prof Whitney's 
writings have taught anything, it is that the sandstone from Sault St. 
Marie to the further side of Keweenaw Point, including the copper- 
bearing rocks, are one and the same formation ; therefore Dr. Hunt's 
statement is incorrect in this particular at least. In proof of this, one 
can read his own statement of Prof Whitney's ideas on page 79 of the 
"Azoic liocks.'* t As we have shown before, Houghton regarded the 
copper-bearing rocks as eruptive in, and therefore younyjer than, the 
sandstone of Keweenaw Point, which in 1843 he took as belonging to 
the "New Red." This is the last published statement that we can find 
of Houghton's on this point. 

Mr. Brooks, in his Report on the Iron Distincts of Lake Superior, J re- 
gards it as proved that the copper-bearing rocks are conformable with 
the Huronian ; the proof was obtained, not from contacts, but from 
their common dip and strike. He also states : " Against and over the 
copper series on the north, abut the horizontally bedded lower Silurian 

sandstones As the non-conformahiliti) of the copper-bearing 

rocks and sandstones is doubted by some geologists, it should perhaps 
be stated that the actual contact was not soon. But the sandstones were 
observed lying horizontal, and affording not the slightest evidence of 

* Trans. Am. lust. Min. Eng., 1. 331-342. 

t Sec. Geol. Survey of reiin. E, Azoic Rooks, Part I. 

% Geol. of Mich., I. 184, 185. 

r , 




disturbance, within a few miles of highlj-tilted copper rocks^ which 
gave every evidence of having been elevated before the deposition 
of the sandstones. So far as my observation has extended, this rule is 
general ; that is, no Lake Superior sandstone, which is unmistakably 
lower Silurian, has ever been found in any position otlier than nearly 
horizontal"; — Will Mr. Brooks visit Presque Isle] — *'and no rock which 
was unmistakably of the Copper series has been seen which was not 

considerably tilted. The fact that certain sandstones belonging to the 
copper series are very similar, if not lithologically identical with some 
of the lower Silurian sandstones, has helped to complicate this question. 
An interesting locality for study in this connection is the west fork of 
the Ontonagon lliver, just south of the Forrest Copper Mine. I am not 
Bure but that it affords an exception to the ride above stated, as at that 
point sandstones, apparently Silurian, dip south at an angle of 45°." 

In Prof Pifmpelly's Report of the Survey of the Copper District,* 
we find but little written by him of geological interest excepting that 
which had been published elsewhere, and referred to in the preceding 
pages.f The sandstone beds on the eastern side of Keweenaw Point are 
said to slope gently to the southeast (L c, p. 1). The cliicf portion 
of the geological work, and about all of any value, seems to have 
been done hy Mr. A. li, Marvine, who, judging from his work, appears 
to have possessed the power of observing well and accurately in the 
field. Only certain portions of his work can bo pointed out here : 
" The conglomerate beds of Keweenaw Point have been generally con- 
sidored as mere local deposits, rapidly fading out in either direction. 
The table would seem to show, on the contrary, that for conglomer- 
ates they are unusually persistent, and that while a bed may thin 
out and lose its character as a conglomerate, it may still exist even 

as a mere seam We gather from those facts that when the beds 

composing the trappcan range were being originally formed, the agen- 
cies, whatever they were, whicli formed what are now tlie melaphyrs, 
ceased to act not only over limited but over extended areas, in one in- 
stance at least over fifty (50) miles, and for periods of time long 
enough to allow of the accumidation of beds of conglomerate from a few 
to over 75 feet — in one instance over half a mile — in thickness." 
(L c, pp. 60, 61.) 

Mr. Marvine points out the fact that much of the amygdaloidal charac- 
ter of these rocks is owing to chemical action upon approximately liomo- 

* Geol. of Mich., Part n., 1873. 

+ Am. Jour. ScL, 1S72, (3,) II. 188-198, 243-258, 347-355; TIL 423-432. 




ecncous rock loiii^ after it was formed, and '' the amvirdulos whicli mark 


this change wore thus slowly developed, and are not the mere fillings of 
pre-existing cavities." Besides this pseudo-amjgdaloidal structure true 
amygdaloidal structure was also pointed out. Concerning the sedimen- 
tary origin of these rocks he remarks : ''But the strongest proof would 
seem to be in the structure of the so-called scoriaceous amvo:daloi(ls. In 
those, patches or balls of amygdaloidal material are associated, even sur- 
rounded by an imperfectly stnttitied material, which is undistinguishable 
from the true fine-grained sandstones. This association is such that it 
seems as if it could in no wise be accounted for by metamorphism acting 
on sedimentary beds, but only by supposing a peculiar mixture of the 
materials at the time of deposition, which mixture is not such as 
sediments assume The fact that in sandstones which are in- 
tercalated between two trap beds the upper parts, for several inches 
from the hanging wall, are often changed as if by heat, while at the 
bottom contact there is no such change, cannot be offered as an ob- 
jection to the metamorphic theory, for it would be in just such regions 
that metamorphism would naturally occur. But the fact that sandstone 
material seems to have entered amygdules near the upper part of beds 
covered by sandstones; that it may fill a well-defined crack extending 
down into an underlying melaphyr, .... or that melaphyr may nearly 
surround pebbles, apparently caught up from an underlying conglom- 
erate . . . . ; these facts, as does the peculiar structure of the scoria- 
ceous am3'gdaloids above noticed, seem to point to a very dilTerent origin 

for the melaphyrs than a sedimentary one As a whole, then, the 

structural features of these beds remarkably resemble those of true lavas. 
They have been affected, however, and to a very great extent, by meta- 
morphism, and this metamorphism has taken place in such a manner, 
has so heiglitened and carried on the original structure, as It were, that 
the ordinary proof of their igneous origin, such as contact changes in 
adjacent sandstones, presence of amygdules, etc., fail, and it seems nat- 
ural to consider this metamorphism as a vera causa for the whole struc- 
ture. Certain extraordinary features, however, as noticed above, seem 
wholly incompatible with this idea, and when considered as true igneous 
rocks in which great and peculiar metamorphism has taken place, all the 
phenomena presented seem to be satisfactorily and naturally accounted 

for These changes, however, have been both very many and verv 

great ; so great, in fact, that, as seen above, when once examined they 
seem almost sufficient to have developed all the pecidiarities of. the beds 
from sedimentary deposits. The practical importance of the recognition 




of this mctamorphism and of a proper understanding of its methods and 
effects, will be apparent when it is recollected that to it is due all the 
economical value the beds possess. The beds as originally formed prob- 
ably contained the elements of its minerals, together with its copper and 
silver, more or less disseminated through their mass, as much so re- 
mains till the present day, or else they were so contained — at least in 
part — in overlying rocks, and in this form they could have been of no 

economic value ; nor could any process taking place at that time have 
concentrated the minerals in the manner in which they now occur." He 
opposes the theory that the copper was deposited in its present position 
by igneous action. 

The metamorphic action is thought to have resulted from the agency 
of percolating waters. *' All the phenomena tend to prove that it is by 


naeans of some such chemical actions as these, continued through long 
periods of time, that the mctamorphism of these beds has been effected. 
It is such metamorphism which has developed the amygdaloidal mela- 
phyrs, formed segregations, modified and filled the veins and amygdules, 
placing in them their minerals in the present relative positions ; and, in 
the general process, the copper, like the other ingredients, was selected 
from its disseminated and therefore useless condition, and concentrated 
in veins, amygdaloids, and conglomerates till it reached a percentage of 
richness that gives to the deposits an economical importance. This 
action has taken place certainly not at a high temperature, and possibly 
at a temperature no greater than that of the beds at present, while it 
may have been largely aided by that electric action which chemistry 
almost always induces, and which is known to be active at the pi'esent 
day. In fact the presence of the latter is proof that chemical action is 

even yet going on 

Where observed, the hanging-walls of the sandstones were generally 


smooth and gently undulating, but occasionally quite uneven, while the 
upper two to twelve inches w^ere somewhat changed, being harder or 

softer, or lighter or darker-colored than the mass of the bed The 

foot-walls are sometimes smooth and undulating ; the surface of the 
underlying bed, when not an amygdaloid, as was sometimes the case, 
seeming to have been worn smooth, as if by attrition; or else the sand- 



In one 

stone seemed to fill inequalities in the underlying amygdaloid, 
sandstones were not observed to be changed near the foot-wall, 
remarkable instance, a crack or fissure was observed extending down 
into a melaphyr, which was filled by the overlying sandstone. The con- 
clusion Is inevitable, that the melaphyr had formed, hardened, and 
cracked before the sandstone was deposited 






" The veins of tlic district were of course formed long after the cou- 
sohdatioii of the beds, and probably when they were being Hfted into 
their present position. They have subsequently been tilled with the 
various minerals which now occupy them, wliolly by iuliltration and 
chemical, probably aided by attendant electric, action, and in a system- 
atic and natural sequence." (1. c, pp. 108 - 115.) 

Eegarding the junctions of the sandstone and amygdaloid in two local- 
ities he says: ''■Junction^ very irregular. For two feet the imderlying 
sandstone is changed and indurated, being, in places, hardly distinguish- 
able from the overlying mclaphyr, except for enclosed pebbles which arc 
not changed. Some pebbles rest upon the hanging-wall, which are quite 

enclosed in tlie overlying amygdaloidal mclaphyr Junction, slightly 

undulating. No change or metamorphism in the adjacent beds. Extend- 
ing from the junction down into the underlying mclaphyr — about 
eight feet being exposed — is a fissure or crack with sharply defined 
edges and two abrupt bends, giving widths of two and four inches. Tills 
crack is filled with sandstone similar to that above, but somewhat finer 
and slightly decomposed or softened. There is an appearance of irregu- 
lar, but rudely curved sti'atification, about parallel, as a whole, with 
the formation." (/. c, pp. 118, 119.) 

It is to be seen, then, that Mr. Marvine arrived at the same con- 
clusions regarding the Copper-bearing rocks as did Messrs. Foster and 
Whitney, and supported these views by the same evidence that they 
had more fully and thoroughly given in their report. 

lu Part 111.* we have the report of Dr. C. Rominger on the Pahc- 
ozoic Hocks. Eegarding the sandstone he says : " The lower Silurian 
age of the Lake Superior sandstone is unequivocally proved by ita 
stratigraphlcal position. In its whole extent it is visibly overlaid by 
calcareous ledges, containing fossils peculiar to the Calciferous forma- 
tion, or, in other cases, by the Trenton limestones. The recognition of 
a separate rock-series, identifiable with the Calciferous formation, at 
once nullifies the other mentioned opinions of Geologists, and leaves no 
choice but to see in the Lake Superior sandstone the equivalent of the 
Potsdam sandstone. . * . . The thickness of the Sandstone formation is 
dilficult to ascertain. Its lower portions are so intimately connected 
with the sandstones and conglomerate beds of the copper-bearing Trap- 
poan series, that I could draw only an arbitrary division line between 
the two groups, which would swell the thickness of the sandstone group 
to many thousand feet, while east of the Copper range, the whole sand- 

* Geol. of Mick., 1, 1S73. 

1 1 



stone series reposing on the Huronian and Granitic rocks does not ex- 
ceed the thickness of 300 feet." {L c, pp. 80, 81.) 

*' The sandstones lining the eastern shore of Kcewenaw Point extend 
approximating to the centre of the Peninsula, retaining their horizontal 
position, and also their lithological characters to such a degree that the 
different strata can be parallelized without difficulty with those of the 
more eastern localities. Near the centre the horizontal sandstone ledges 
arc found at once abutting agahist the uplifted edges of a difTerout rock- 

which form the most elevated central 
" The discordance of the strata 
on the east side of the axis of elevation; and their conformability on the 
sloping west side, finds its explanation in the hypothesis of a gradual 
submarine upheaval of the trap range, in its subsequent rupture, and 
the final emergence of the western margin from the water, while the 

scries — the Copj^/er-bearmg rocks — 
crest of the Peninsula." (L c, p. 95.) 


eastern portion of the fissured earth's crust remains submerged." (/. 

p. 98.) 

In 1874, Prof. Roland Irving discusses the question of the age of 
the copper-bearing rocks of Wisconsin, which were regarded as iden- 
tical with those of Keweenaw Point. He advocates the same views 
as those held by Pumpelly and Brooks, and bases his conclusions on 
simiLar grounds. The Laurentian, Huronian, Copper-bearing rocks, 
and Lower Silurian sandstones were never seen in direct contact with 
one another with one exception. That exception is the junction of a 
trap supposed to belong to the Copper-bearing series with the Potsdam 
sandstone. The sandstone, he states, is for three hundred feet from tiie 
trap *' broken in every conceivable manner, the misphieed layers dipping 
in all directions, and in its immediate vicinity making a sort of brecciatcd 

mass of fragments of trap and sandstone These trappeau beds 

carry here no intercalated beds of sandstone and conglomerate.'' He ob- 
jects to the most probable explanation in this case, the protrusion of this 
trap through the sandstone, as the trap seems to be unlike the Copper- 
bearing rocks, except in the fact that it is an old basalt ; but thinks 
some deep-seated force shoved the old formation, on whose ffanks the 
sandstone was deposited, upwards, and so produced this dislocation.* 

Concerning the relation of the western sandstones to the eastern and 
to the trap rocks in the Ontonagon district, Dr. Rominger says : "The 
age of these beds is intermediate between the trap and the horizontal 
sandstone deposits; but between all three of the indicated groups so great 

* Am. Jour. Sci., (3,) VIll. 46-56; Trans. Wise. Acad. Sci., 1873-74, IL 

« » 



lithological affinities exist, that it is most natural to consider them as 
the consecutive products of one and the same epoch, in the commence- 
ment of which the just-formed strata M'cre displaced by volcanic action, 
which subsided toward the end and loft the last deposits undisturbed." * 
In 1878, Prof. Pumpelly published a paper entitled the " Metaso- 
matic Devolopmont of the Copper-bearing Rocks of Lake Superior." f 
This is devoted principally to a description of the microscopic characters 
of these rocks and their alterations, and, although we differ in nomen- 
clature, we regard it as one of the very best papers published upon mi- 
croscopical lithology. His geological ideas remain the same, however, as 
he states that the greater age of the Keweenaw series over the Potsdam 
sandstone is proved by abundant evidence of non-conformability. He 
regards them " more nearly conformable to the underlying highly tilted 
Huronian schists. They are thus the product of the earliest eruption 
of basaltic rocks to which a proximately definite ^age can be assigned. 
They were preceded by very extensive eruptions of acid rocks, especially 
porphyries. These basaltic rocks have been subjected to a wide-reaching 
alteration, which has produced marked changes in the internal condition 
of the beds, and has filled the fissures with a rich variety of minerals, 
whose constituents were derived from the products of this alteration. 
{I. c, pp. 253, 254.) These old basaltic rocks were considered to be 

melaphyrs and diabases. 

It is to be seen that he now adopts the views of the origin of the 

traps held by Messrs. Foster and Whitney, and later by his assistant, 

Marvine. The reasons for this radical change of base are not stated : 

we have simply the assertion that the traps are basaltic overflows, made 

us though no one had ever held a diiferent opinion. 

Later, Dr. T. Sterry Hunt says that it seems probable from our pres- 
ent state of knowledge that the traps are of volcanic origin. He re- 
gards them as unconformable with the Huronian, as he takes the 
Copper-bearing rocks as the ecpiivalent of his Taconiau. This, of course, 
requires the intercalation of his Montalbau between them and the 
Huronian. t 

Dr. J. D. Dana in his Manual of Mineralogy and' Lithology,§ says 
concerning the occurrence of the native copper with disseminated silver : 
" This mixture of copper and silver cannot bo imitated by art, as the 

* Geological Survey of Micliigan, 1873-1876, HI. 154. 
t IVoc. Airi. Aeaduiny, XIII. 253-309. 
t Sec. Geol. Survey Pemi. E, Azoic Kocks, Part I. p. 236. 
§ Kcw York, 1878, p. 131. 



two metals form an alloy when melted together. It is probable that 
the separation in the rooks is due to the cooling from fusion being so 
extremely gradual as to allow the two metals to solidify se2)arately, at 
their respective temperatures of solidification — the trap being an igne- 
ous rock, and ages often elapsing, as is well known, during the cooling of 
a bed of lava, covered from the air." We may remark here that Hunt's 


edition of Ure*s Dictionary, 1878, states that the West Canada copper 

mines are the most important iu America. Such carelessness of state- 
ment should hardly be allowed in a work of its purported character- 
Mr. A. R. C. Selwyn, in the Canadian Naturalist,* opposes the use of 
the numerous names based upon purely theoretical hthology ; i. e. No- 
rian, Montalban, Taconian, Kewccnian, etc., in the crystalline rocks. 
He includes the Copper-bearing rocks in the Huronian. His views, how- 
ever, were objected to by Mr. Thomas Macfarlane.f Mr. Sclwyn's paper 
"was again published in the Report of Progress of the Canada Geological 
Survey for 1877 - 78 (A, 15 pp.). 

In the third edition of Prof J. D. Dana's Manual of Geology (p. 778) 
we are given his views concerning the deposition of the copper at Lake 
Superior as follows : " When eruptions of melted rock have taken place, 
fliey have often brought not merely the heat of great depths to tho 
surface, but also, various mineral materials encountered on the way up, 
and especially some of the metals or their ores. 

*' The fissures were in general deeper than those that gave origin to 
veins of segregation, for the latter did not reach to where melted rock 
could fill them, and hence had to be filled by Avliat they could 
get through the slower process. They consequently nmst have de- 
scended to regions of very high temperatin^e. As in a volcanic conduit, 
■whatever at these depths, in the heated subterranean region adjoining 
the opened passage-way, was ready to pass into a state either of vapor 
or liquidity, would have been forced, by the pressure to which it was 
subjected at those depths, to escape, if possible, by the way made for 
the liquid rock, and would have ascended either along side of the latter, 
or within its mass; and -at the same time, a portion would have been 
liable to be forced into the wall rock of the fissure wherever it was not 
of too close a texture to receive it. The mineral material that could take 
advantage of such an opportunity, or be aided in it by the heat of tho 
ascending melted rock, would be that, as just implied, which was most 
easily fused or vaporized ; and this includes certain metals and their 

* 1879, {2,) IX. 17-32. 

1 Remarks on Canadian Stratigraphy, Can. Nat. and Geo!., (2,) IX. 91 -102. 





ores, especially those of copper, silver, and antimonlal, arsenical, and 
sulphurous ores of lead, or of lead with silver or copper. The fusing 
points of pure copper and silver are below 2,500° F., that of copper 
being, according to Kiemsdyk's experiments, at the Utrecht mint, in 
18G0, 2426° F. and that of silver, 1904° F.; and hence these might have 
passed into the melted rock in the liquid state; but whether this was 
the fact, or whether they were in vapor, or in some vaporizable or solu- 
ble compound, is not definitely known. 

" The above is a general explanation of the initial movement in tha 
making of copper mines like those of Lake Superior, in which the 
metal is in the native state, and the silver mines of Nevada, Mexico, 
Bolivia, Chili, Transylvania, and of many other regions, which afford 
various ores of silver with often some native, silver. The igneous rock 
of the Lake Superior region is largely doloryte, and copper is in fissures 
and cavities in the igneous rock, and in the sandstone of the walls." 

In the third volume of the Geology of Wisconsin the copper-bearing 
rocks are regarded as oldei; than the sandst9ne, but younger than the 
Huronian. The traps, with their associated sandstones and conglom^ 
erates, are called the ICeiveeiiawan series, while the supposed unconform- 
able sandstone is regarded as Potsdam. The evidence advanced is good, 
so far as it goes, but it proves nothing until it shall be shown that the 
old basalts studied in each particular case are not dikes, but overflows 
identical in age with those on Keweenaw Point, and that they are not 
earlier or later eruptions. In this respect the strongest evidence ad- 
vanced by the Wisconsin geologists is fatally defective. Their methods 
of observation fail in giving the proof necessary to establish their cou- 
clusions, which may or may not be correct, so far as their work goes; 

Historical Summary. 

The theories advanced concerning the Copper district are so various 
and conflicting, in many cases even in the writings of the same author, 
that we cannot hope to do justice to them in a brief summary. 

The principal points to which we have directed attention thus far are : 
1st, the origin of the traps and their interbcdded sandstones and con* 
glomcratcs; 2d, the relation that the traps bear to the eastern and 
western sandstones ; 3d, the age of the eastern sandstone ; 4th, the 
origin of the veins and the copper deposits. 

Concerning the origin of the traps, it has been seen that they were 
said to be in dikes, generally intruded through the series of sandstones 



and conglomcrateSj by Houghton, Jaokson, Sheparcl, Hubbard, and Mar- 
cou. They were thought to bo in hiva overflows by Hubbard, Foster 
and Whitney, Jackson, Bigsby, Hall, Hunt, Pumpelly, and Irving. 
They were regarded as metamorphosed scdhnentary rooks by Locke, 
Eivot, Pumpelly, and Brooks, while the amygdaloidul portion was said 
to have been formed from fused sandstone by Ilonghton and Jackson, 
and from sedimentary material, possibly volcanic mnd, by Hunt. The 
latter author at first taught that the traps were eruptive, but separated 

the amygdaloids from them. 

The traps were supposed to be of a prior age to the sandstones by 
Bayfield (who thus long antedated the views of Pumpelly and Brooks), 
Logan, Whittlesey (who regarded them as conformable with the sand- 
stones), Alexander Agasslz, Pumpelly, Brooks, Hunt, Rominger, Irving, 
and Selwyn. They were said to be younger than the sandstone by 
Houghton, Jackson, and Marcou. They were taken to be of the same 
geological age as the sandstones by Hubbard, Foster and Whitney, 
Jackson, Bigsby, Pivot, Logan, Hall, Dana, Pumpelly, Hunt, and Pom- 


The traps were assigned to a geological age distinct from the eastern 
sandstone, and given the name Keiveenawan- by the Wisconsin geologists, 
Keweenawian by Brooks, and Keweenian by Hunt. Logan and Selwyn 
assigned them to the Iluronian, the latter doing so principally on ac- 
count of the erroneous observations of Pumpelly and Brooks. 

The eastern sandstone of Keweenaw Point was regarded as Old Ped 
by Bayfield and Bigsby ; as New Ped, by Houghton, Puggles, Jackson, 
H. D. Rogers, Shcpard, Owen, Marcou, and Dana; as Potsdam, by Hub- 
bard, Foster and Whitney, Owen, Logan, Hall, W. B. Rogers, Pivot, 
Rominger, and Irving ] as partly Potsdam and partly Calciferous, by 
Logan and Dana; as Calciferous, by Dana; as Chazy, by Logan; as 
Quebec, by Logan, Hunt, and Pumpelly ; as Permian, by Macfarlanc ; 
and as Permian or Triassic, by Bell. The sandstone was also thought 
to be older than the Potsdam by Logan and Whittlesey. 
■ Dr. Houghton at first regarded the sandstone and trap from the Sault 
St. Marie to the Porcupine Mountains as the same formation ; later, he 
thought that the sandstone west of Grand Island was nnconformably 
overlaid by that east of that island ; still later, the saiKlstones oast of 
Keweenaw Bay were said to be older than the Trenton, while the Cop- 
per-bearing rocks were thought to be New Red. 

The veins were thought to have been formed anterior to the traps by 
Jackson, and at the time of their eruption by Dana and Marcou, but by 




tlio majority of the observers posterior to the consolidation of the entire 
series of rocks. They were believed to have been filled by injection by 
Houghton, Ruggles, Jackson, Agassiz, and Marcou ; by injection and 
sublimation, by llodge ; by sublimation, by Houghton and Jackson ; and 
in the wet way, by Foster and Whitney, Eottermund, Muller, Bauer- 
man, Dawson, l*umpelly, Marvine, Hunt, and others. Houghton re- 
garded the district as identical with Cornwall. The copper was 
supposed to have been thrown from volcanoes by Schoolcraft, while 
H. D. Rogers and Dana teach that it was deposited during the cooling 
of the trap. Kuggles, Agassiz, and Marcou regard it as injected in 
dikes from the molten interior, while Baucrman and Pumpelly teach 
that it was originally deposited in the sandstone from the sea-water 
through the reducing agency of organic matter. This view seems to be 
shared by Hunt, who likewise, in connnon with Shepard, thought that 
copper was derived from the debris of ores in the older rock^, and depos- 
ited in tlie sandstones. Prof. Shepard thought that it was concentrated 
from the sandstones, and brought to the surface by the action of the 
traps. Whether Dr. Hunt teaches that tlio copper was derived directly 
from the sandstones and deposited in the veins, or was brought up by 
the extravasated traps, which, according to his theories, must have 
originally formed the lower portion of the Keweenawan series, and w\a3 
thence concentrated in the veins, we cannot tell, for, . is frequently 
the case in his Avritings, his English admits of more than one construc- 
tion. Muller, Bauerman, and Marvine think that the copper may have 
been an original constituent in the traps in a finely divided condition. 
Prof. Dana teaches that it was derived from ores in the older rocks 
by the action of the traps, and holds, with Houghton, Jackson, and 
Sliepard, that it was brought up by the trap. Foster and Whitney, 
Dawson, Muller, Bauerman, Pumpelly, Marvine, and others, would refer 
the concentration to electro-chemical action. Benjamin Silliman, Jr., 
and Jackson said that the copper and silver, when found joined, had 
been fused together ; while Hodge explained the phenomenon by sup- 
posing that the copper was injected first, and by its contraction left 
vacant spaces into wdiich the silver was injected later. Such, in brief, 
are some of the various theories advanced. 

V i 

The Traps. 

In order to ascertain the origin of these rocks, we have to examine, 
first, their relation to one another, and, second, to the interlaminated 
sandstone and conglomerate. 



The relations of these rocks can be well stndied in an adit about one 
mile long, extending from the western sandstone' through alternating 

"beds of sandstone, conglomerate, and trap, to the ash-bed at the Cop- 
per Falls mine. We find here that the sandstone, when* underlying 
the trap, has its upper portion adjacent to it baked and indurated ; 
showing the usual characteristics of a ferruginous sandstone when 
subjected to a certain amount of heat. This indurated sandstone has 
frequently been subjected to secondary water action since it was buried 
under the trap, and hence has lost some of its hardness and other signs 
of baking. No fragments of the trap were foimd in the immediately 
underlying sandstone, but tongues of trap extend down into it in some 
places, and indurate it. The surface of the trap underlying the sandstone 
is water-worn, forming smooth, rounded knobs and irregularities, upon 
■which the sandstone "was deposited. The immediately overlying sandstone 
shows none of the baking and induration that the underlying one does. 
In no case, so far as w*e saw, was there any difficulty in separating the 
sandstones or conglomerates from the traps. The upper side of the 
sandstone was especially distinctly separated from the overlying trap, 
while on the under side, on account of the composition of the sandstone, 
the junction was not so obvious. While the trap always affected its 
underlying sandstone, and frequently included "masses of it, in no case 
did it produce any effect on the overlying one. The sandstones or con- 
glomerates at their base contain fragments and pebbles of the under- 
lying trap ; but this detritus diminishes as we recede from the trap, and 
is generally wanting after a thickness of two or three feet has been laid 
down. The trap is found to be cellular and amygdaloidal on its upper 
side, but on the lower to be compact and more coarsely crystalline. If 
the traps had been intrusive between the beds of sandstone, both the 
upper and underlying sandstone would be alike affected adjacent to the 
trap. If the trap was formed from the sandstone metamorphosed 
in dt'ti there ought to be some gradual passage between the two, and 
the fragments of sandstone enclosed in the trap should more especially 
show such passage. On the contrary, nothing of the kind could be 
found, but the sandstone fragments w^ere greatly indurated, and the 
traps adjacent to them filled with quartz (64G, G47, G48). Specimens 
469, 478, 479, 480, 482, and 483 from the Calumet and Heck, and 021 
from the Copper Falls mine, are examples of the contact of the stuid- 
stone with the underlying trap, and 477 and 473 from the Calumet and 
Hecla, and 577, 578, 579, 610, 611, 612, 613, and 620 from Copper Falls, 
show the contact with the overlying trap. The only explanation of 



? ! 



these facts, wlilch were first pointed out by Messrs. Foster and Whit- 
ney, and later by Mr. Marvine, is that given by them, that the traps are 
lava flows, and that they were successively laid down upon one another, 
or covered by sandstone and conglomerate. They are seen to have the 
same characters, except so far as they have undergone secondary changes, 
that modern basaltic lavas have. These old basalts have been denomi- 
nated mclaphyrs and diabases by Prof. Pumpelly, to whom lithologists 
are indebted for their knowledge of their microscopic characters. While 
we would use the terms that Prof. Pumpelly has, we object to the ap- 
plication he has made of them. Many of his diabases we should call 
mclaphyrs, and many of his melaphyrs wo should class as diabases. 
We of course differ in our dofmitions of these terms, for wliile he would 
regard melaphyr and diabase as distinct rock species, we hold that they 
are only altered forms of basalt. The greenstone ridge back of the 
Cliff and Phoenix mines we regard as an excellent example of diabase 
(791, 792), with whicli we class all the hcavy-boddcd crystalline traps 
of that region, while the thin-bedded scoriaccous or amygdaloidal highly 
altered traps wo class as melaphyr, but in the majority of cases Prof. 
Pumpelly regards them as the reverse. The diabases are rarely if ever 
mined, the mclaphyrs frequently. 

In a recent paper "On the Carboniferous Volcanic Rocks of the 
Basin of the Firth of Forth — their Structure in the l.eld and under 
the Microscope,"* Prof. Geikie points out the difference microscopically 
between lava flows and intrusive masses, and evidently thinks that 
they can always be as readily separated in the cabinet, microscopically, 
as they can be' in the field. While it is doubtless true that this sepa- 
ration can be made in the rocks, studied by Prof. Geikie, his distinc- 
tions fail in the Lake Superior district. The difl'erence in structure 
pointed out by him seems to be entirely owing to the rate 'of motion 
and pressure at the time of crystallization, and the rapidity with Avhich 
the lava solidified. When lava flows in thin sheets, or, if we con- 
fine our examination to the upper portion of a thick sheet, we find 
characters that readily distinguish the sheets from the dikes ; but when 
we come to study the middle and lower portions of the thick sheets, 
where there was little or no motion combined with the pressure of the 
overlying mass, the rock is undistinguishable from rock of the same 
composition in dikes ; and tlie diagnostic characters given by Prof 
Geikie would assign it to an intrusive rock,: not to an overflow. In the 
before-mentioned Emerson adit at the Copper Falls mine, some mela- 

# ' 

Trans. Koyal Soc. of Ediiilmrgli, XXIX. 437-518. 



has attracted considera- 

phyrs were seen that were apparently in the form of dikes intruded 
since the lava flows (624, 626, 627, 628). 

The form of lava locally known as " ash-bed ' 
ble attention. It has been described in various ways, generally being 
regarded as fused sand and trap. Latterly Prof. Pumpelly has described 
this as "volcanic scorise buried in the littoral sand."* At the present 
time the ash-bed can be best studied at the Copper Falls mine, whore it 
is largely mined for the copper it contains. After a careful study of it, 
we conclude that the ash-bed is a very scoriaceous, and, conjparatively 
speaking, somewhat thin lava flow. It does not possess the ordinary 
characters of the other flows of Keweenaw Point, but seems to be largely 
made up of clinkers and scoriaceous masses. It appears to have flowed 
in a more or less fragmental condition, forming a black, rough, loosely 
aggregated, scoriaceous, cinder and lava sheet, similar to those described 
by Prof. Whitney in his "Report on the Geology of California," f and 
by Prof. Palmieri in his "Account of the Eruption of Vesuvius of 

1871-72." + 

At the time of the flow, or since, the interstices were filled with de- 
trital mud. The various parts of the flow seem to be connected in the 
main, and do not form to any great extent true pebbles. 

That the rounded fragmentary portions derive their structure from 
the cooling of a fluid mass, and not by water action on the melaphyrs, 
is shown by their cellular structure in the interior, and solid crust on 
the exterior, the same as similar modern lavas have. Water-worn peb- 
bles of melaphyr, as seen at some of the old burrows of the Hancock 
mine in a detrital deposit (832, 833), which to the casiuil observer 
resembles the ash-bed, have the cellular structure extending throughout 
the mass, and are destitute of any crust. 

The saAie flow exists at the Petherick and Old Phoenix mines, while 
a similar formation is mined at the Atlantic. Besides the true ash-beds, 


there seem to te confounded with them certain sedimentary deposits 
composed of rotmded water- worn pebbles of melaphyr held by littoral 
,sand. These forms pass- into a more siliceous conglomerate or sand- 
stone, or not, according to the length of time that elapsed before the 

They are abundant west of Houghtf#i, and, so far as 
I could find, are the only formations existing at the Hancock mine that 

* Proc. Am. Acad., XIH. 283. 

t 1865, Vol. I. p. 267. 

4 Annali del reale Oascrvatorio meteorologico Yesvaviano, (Napoli, 1873,) p. 28. 
The same, translated by Robert Mallett, (London, 1873,) p. 103. 

succeeding flow. 


• • 



could have lod Prof. Pumpcllj to state that an ash-bed was worked 
there.* Specimen 814 is a good example of the end of a lava mass, 
which still retains its original ropy and lluidal surface structure. This 
came from the ash-bed at Copper Falls, a^d gives conclusive evidence 
that it had never been water-worn. Tongues of the ash-bed were seen 
extending down into its tuiderlying trap, while the overlying trap sends 
tongues down into the ash-bed (Fig. 27). 

From their nature all the various lava flows are liable to be limited iu 
any direction, either from their thinning out, the flow meeting obstruc- 
tions, or from denudation since deposition, but before being buried under 
conglomerate or the succeeding flow. They were evidently poured out 
on a shore line, whose position probably varied relatively to the traps. 
The intervals between the different flows seem to be brief in some cases, 
while in others- considerable time must have elapsed. Figure 28 shows 
the relation of the trap to the sandstone at one point in the Emerson 
adit at Copper Falls, exhibiting the irregular surface of the latter before 
the lava flow. 

The Sandstones and Conglomerates. 

As wo followed the Ilungarian River, a tributary of Torch Luke, np- 
ward, starting from the low sandy pkins near the lake, the sandstone 
was first observed forming high bluffs on both sides of the river, and 
dipping N. 45° W. 10°. It occurs in coarse and fine layers often en- 
closing pebbles. As the river is ascended the layers of pebbles were 
seen to curve in various directions with an irregular dip, but which in 
general inclined to the northwest. Some of the pebbles appeared to bo 
of quartzite similar to that at Carp River, Marquette (522). The Hun- 
garian Falls are formed by the river being precipitated over several 
ledges of the sandstone and conglomerate. Several specimens were 
taken, showing the different varieties of pebbles composing the con- 
glomerate (523, 524, 525, 526, 527, 528, 529, 530). No. 523 is an old 
trachyte composed of a reddish-brown groundmass, holding white kao- 
linized feldspars, dark brown decomposed hornblende crystals, and a 
little mica. It is closely allied to some of the modern rocks from the 
Cordilleras. The groundmass is now kaolinized, forming a dirty-white 
mass holding secondary quartz and feldspar, as well as long narrow 
ferrite masses. These latter appear to have been formed from the horn- 
blende fibres, so frequently seen in the allied rocks from the Cordilleras. 
The groundmass has now through its alteration a spherulitic structure. 

i: . 


VOL. VII, — NO. 1. 

* Proc. Am. Acad., XIII. 283. 




No. 524 is a more compact rock of like cbaractei'. Its groundmass is 
kaolinized and holds the quartz and feldspar alteration products. It 
is filled with grains and masses of fcrrite probably derived from Lorn- 
blende. The feldspar is so decomposed that it cannot be told whetlicr 
it is plagioclase or orthoclase, Nos. 52G and 529 are like No. 523, 
while No. 530 is more allied to No. 524. 

No. 527 has a more coarsely crystalline, granitoid structure, showing 
under the lens a reddish and grayish brown groundmass, holding elon- 
gated brownish-black hornblende crystals. In the thin section it is 
seen to be composed of feldspar, magnetic iron, horublendo, and some 
quartz. The feldspar is greatly altered, and is now composed of inter- 
growths of feldspar and quartz, giving rise in it to a structure resem- 
bling that of graphic granite, or much of that figured as belonging to 
the Eozoon Canadcnse. The quartz is all secondary, and the hornblende 
altered to reddish or yellowish brown ferruginous masses. 

No. 528 is a fine-grained granitoid trachyte (granite porphyry), but 
in the thin section the feldspar is seen to be so altered and filled in with 
secondary quartz, containing full and bubble-bearing fluid, and vapor 
cavities, that the section resembles that obtained from some fragmcntal 
rocks. No. 525 is a rock of similar character. 

Nos. 538, 539, 541, and 544 are good examples of some of the sand- 
stones on the river below the melaphyr. No. 538 is seen in the section 
to be composed of quartz and trachytic detritus. 

Below and at the base of the falls the dip remains the same as before, 
N. 45° W. 10°, but above tliis locality the inclination varies, rising from 
15° to 18° between the first and second falls. In some places a qua- 
quaversal dip was seen. Some five falls exist in the river, and at the 
last or upper fall the melaphyr was found. The dip of the sandstone 
has now increased to some 20°, but still dips northwest, and the first 
trappean flow is seen to overlie and greatly indurate and alter it. This 
immediately underlying sandstone (537) is filled in with little reticulated 
veins of calcitc, a! kaolin-like material, etc., and in general resembles tlie 
baked sandstone found underlying the trap on the western side of Ke- 
weenaw Point. Microscopically, it is seen to be composed of the debris 
of the trachytes previously described. This sandstone was seen within 
three inches of the melaphyr, and although there may have been some 
eliding motion between the two, as the contact was not seen, yet the 
induration of the sandstone, its dip, and its relations to the melaphyr, 
prove that it underlies the latter, which flowed over it. This, then, 
■with evidence obtained on the Douglas Houghton Kivcr, settles the 



long-disputed quostiun of the relative age of the traps and eastern sand- 
stones of Lake Superior. The dip of the nielaphyr is about the same as 
that of the sandstone. Immediately above this thin lava sheet, a con- 
glomerate comes in, forming the fifth fiilL The base of this conglom- 
erate is composed of a fine-grained detritus formed from the melaphyr 
and trachyte, and holds numerous pebbles of the melaphyr, as well as 
of the other rocks (531, 532, 533, 534, 535, 536). Immediately over- 
lying this conglomerate is another melaphyr flow, and we have here on 
the eastern side a repetition of the same alternate bands of melaphyr 
and sandstone that occur on the western side. 

It is to be remembered that Mr. Agassiz, in conjunction with Mr. 
L. (I. Emerson, the well-known mining engineer of Hancock, and at one 
time assistant on Prof. Pumpelly's geological survey, found below the 
Douglass Houghton Falls pebbles of the melaphyr (amygdaloid) in 
the sandstone; and from this the conclusion was drawn that the sand- 
stone was younger than the trappcan formation. At the time of our 
visit to this locality, we had no knowledge of Mr. Agassiz's observa- 
tions,* except from the general statement of Prof. Pumpelly.t It will 
be seen that no localities were given by Prof. Pumpclly, although he con- 
firms Mr. Agassiz's statements. The falls were said by Mr. Agassiz to be 
located at the junction of the sandstone and trap, while on both sides 
of the ravine the horizontal sandstone beds were traced up to the falls. 
Our examination showed that immediately below the falls sandstone 
and conglomerate exist, dipping N. ib"" W. 25° (504, 505). While the 
majority of pebbles were of the usual character, one grayish granitoid 
pebble (50G) containing epidote was obtained. This has suffered the 
same graphic alteration in Its feldspar that No. 527 has. Much of the 
feldspar is seen to bo triclinic. Otherwise than its containing more 
quartz, its characters are in the main like No. 527. The sandstone, at 
its junction with the overlying trap, is much indurated and altered, and 
specimens were obtained showing the junction of the two (507, 508, 509, 
510, 511). As the sandstone underlies tlic trap, it is of necessity the 
prior-formed rock. Wo suppose that this was the locality at which 
Messrs. Agassiz and Emerson obtained their specimens of melaphyr in 
the conglomerate. If so, it is easily enougli explained, for conformably 
underlying this sandstone is another sheet of melaphyr, then more sand- 
stone, again more melaphyr, and so on, all conformably underlying one 
another as much as they do anywhere within the trappean belt, or can 

* Proc. Bost. Soc. Nat. Hist., XI. 214-246. 
t Geol. of Mich., Part H. p. 3, 

i ! 



do,- on account of their origin. Whether this is the spot or not, it is 
evident from the language of Mr. Agassiz's paper that the gentlemen 
took their facts and drew their concUisions while they were within the 
trappean belt, not having found the junction at all, it being some dis- 
tance below the falls, not at them. From Prof. Pumpelly's state- 
ment it would seem that he had made the same mistake, as likewise 


Mr. Foster had done years before.* Something more is necessary to 
be observed than simply to find a sandstone or conglomerate on the 
eastern side ; it is necessary to pi'ove that it is part of the eastern sand- 
stone, and not a bed intercalated' in the trap. The sandstone and mela- 
phyr, a short distance below the dip last given, has a dip of 20°, still 
inclining to the northwest. The last melaphyr sheet underlies a sand- 
stone dipping at this angle, and is itself underlaid by another sandstone 
having the same dip. In other words, the last trap on the eastern side 
of Keweenaw Point is a thin flow of only some two feet in thickness, at 
this locality, and is intcrbedded between sandstones which innncdiately 
above and below^ it have the same dip that it has. As the river is fol- 
lowed- downwards the dip gradually declines in steepness, although still 
dipping northwest. The last dip measured was N, 45° W. 5^ The 
conglomerate and sandstone below the first basaltic flow, i. e. that near- 
est to Torch Lake, has apparently been acted upon by hot waters. The 
sandstone has been leached, its fcldspathic constituents largely changed 
into clay, luul the pebbles are greatly altered and kaolinized. The con- 
stitution of the sandstone and conglomerate appears to have been origi- 
nally the same as that of the bands intcrlaminatcd with the trap, except 
80 far as they fire modified by the detritus of the latter. In many places 
tliis hot-water action has bleached the sandstone and leached out of it 
all the argillaceous material, leaving it a nearly pure siliceous sandstone 
(518). This h:is also converted some of the finer beds into a fine-grained, 
hio-hly ar^/dlaccous sandstone or arenaceous clay, these beds having prob- 
ablv arrested the progress of much of the argillaceous material (519, 
520). This water action would certainly account for the absence of fos- 
siliferous I'emains in the'sandstone exposed to its effects. Considerable 
mica in fine scales was seen in the argillaceous bands. Specimeus of 
the various pebbles were taken from the conglomerate (513, 514, 515, 
516, 517). No. 517 is a grayish and rcddishdjrown granitoid-looking 
rock, and under the lens is apparently composed of feldspar holding 
quartz grains. Microscopically it is seen to be a crystalline aggi'egatc of 

* Smiatc Docs., 1st Sess. 31st Cong., 1849-50, 111. 782 ; Executive Docs., Ut 
Sess. 31st Cong., 1849-50, IX. Doc. G9, p. G7. 





decomposed feldypar and hornblende, holding much secondary quartz. 
The quartz is arranged in tlie feldspar in the graphic or eozoon form, 
which makes the decomposed feldspar a most beautiful object in polarized 
light. The contrast between the bi'illiantly polarizing quartz and the 
feebly polarizing, kaoliuized feldspar substance is thus strongly brought 
out. The quartz appears to have been deposited from the decomposed 
feldspar itself, which breaks up into silica and the kaolin-like material. 
The quartz contains full fluid cavities, those with bubbles, and vapor 
cavities. The hornblende is in the usual reddish-brown decomposed 
masses. Some magnetite was seen. This rock is most probably a de- 
composed old trachyte, although it would doubtless be regarded as a 
granite porphyry by most litliologists. No. 515 is a similar but more 
felilspathic rock. No. 513 is similar to No. 527, and Nos. 514 and 516 
are like No. 524. Many pebbles or lenticular masses of clay were seen, 
that arc apparently decomposed pebbles of the conglouierate. 

lu the sandstone quarry at the head of the incUne on the Hecla and 
Torch Lake Railroad, the sandstone layers have been regarded as being 
nearly horizontal. The joint planes that form the floors of the quarry 
are nearly so, having only a slight dip to the northwest ; but those joint 
planes cannot be the bedding planes, for we find on close examination 
that numerous layers of coarser material, pebbles, clay masses, etc. occur 
in the rock. These layers extend for long distances through the sand- 
stone, and are always parallel, having the same dip, which is N. 45° 
W. 15°. These of course, from their character and regularity, must 
mark the old planes of bedding, while the generally supposed bedding 
planes are secondary joint planes cutting the bedding planes at a small 
angle. This sandstone (456, 457, 458, 459, 4(51,462,463,464) has 
been leached and acted upon by water the same as that below the Doug- 
lass Houghton Falls, and its feldspathic material converted into clay or 
entirely removed. Part of the materials comp(»sing the sandstone, espe- 
cially in the coarser portions, are similar to those in the sandstone at 
Marquette. The quartz grains are partly water-worn, but a large pro- 
portion arc seen to be short crystals formed of the hexagonal prism, 
terminated on both ends by the pyramid, or the usual form found in the 
acidic porpliyritic rocks. It appears, then, as the facets of these crys- 
tals are comparatively unworn, that tlioy were derived from the destruc- 
tion or decomposition of traohytic and rhyolitic rocks (granitic and 
quartz porphyries), the feldspathic material hriving been removed since 
by water, leaving a quartzose sandstone. It is a question worthy of 
examination whether any other sandstones have been formed from • 







acidic volcanic material, from which nearly all the other parts of the 
rock have been removed by percolating waters ; especially as other sand- 
stones have been said to be composed of quartz crystals. 

As the sedimentary rocks are more and more studied, the evidence 
comes on every side that, like this sandstone, while their formation may 
have taken as long as is generally supposed, they may have been de- 
posited very rapidly, some being composed of old volcanic scoria, ashes, 
and mud. In very many other cases the supposed sedimentary rocks 
are really volcanic flows or intrusive masses. In the sandstone just de- 
scribed the same masses of clay (460) occur as on the Douglass Hough- 
ton Eiver, and they may arise here, as there, from the decomposition of 
the enclosed feldspathic or argillite pebbles. Another solution of the 
question of the origin of some of these would be the filling in of cavities 
formed by the removal of some other material, by the argillaceous mate- 
rial brought from above. This is suggested 'by the finding of stalactites 
of the sandstone (464) extending down into the clay. At the spring just 
above the quarry the sandstone (521) is red spotted with white, and 
dipsN. 45°W. 14^ 

The relations of the traps to the interbedded sandstones and conglom- 
erates have been given before. The trap has, when covered by the sand- 
stone, been worn by water, and the latter rock deposited upon it. The 
sandstone^ in its lower portion, holds to a greater or less extent the 
debris of the underlying trap. Should we apply then rigorously the 
logic of the Michigan and Wisconsin geologists, we should make a dis- 
tinct geological age every time a bed of sandstone or conglomerate was 
formed over any of the trappean flows, 

would prove that the Keweenaw series is made iip of some forty to sixty 
different geological ages, every one as distinct from the age of the rocks 
underlying it, as they would niake the Potsdam sandstone distinct from 
the Kewcenawan. 

Besides the melaphyr pebbles and detritus, the conglomerates are 
composed of similar pebbles to those found in the conglomerate of 
the eastern side. No. 552, from the Hecla mine, has a dark reddish- 
brown groundmass, holding white and pinkish feldspars and quartz. In 
the thin section it is seen to be an old rhyolite, and to have flowed as a 
lava, for it possesses the contorted, twisted, fluidal structure seen in so 
many of the rhyolites from the Cordilleras, with which it can be per- 
fectly parallelized, except so far as the alteration has removed some of its 

Their method of roasonine: 

original characters. 

It shows the same twisting and interweaving of the 




brownish^colored glassy material that they do ; its quartzes are fissured 




and rounded, and penetrated bj the base the same as they are in mod- 
ern rhyolitcs ; and in like manner they are seen to be of prior origin to 
the consolidation of the lava. The quartz here, as in the rhyolites, plays 
the same part that oli\^iuc does in, the basalts and hornblende in the 
andesites. It is a foreign ingredient, of prior origin to the lava, and 
has not crystallized out of it.* The quartz contains stone, vapor, and 
fluid inclusions. The majority of the fluid and vapor (empty) cavities 
are arranged along fissures, as if they had been formed by hot waters 
depositing silica in fissures. The feldspar is thoroughly kaolinizcd, 
and, like the quartz, is frequently in rounded and broken pieces, 
which show that it was formed prior to the consolidation of 'the lava. 
Considerable secondary quartz occurs in the groundmass, but the base 
affects polarized light but little, if at all. 

It is intended to figure this section in connection with some of the 
rhyolites of the Cordilleras, for if ever a section showed conclusive 
proof that the view, that volcanic action did not commence until the 
Tertiary epoch, is fallacious, this is one. No. 553, from the same locality, 
has a similar, but lighter brown and less abundant groundmass. This 
holds numerous yellowish-red and clay-colored feldspars, as well as much 
quartz. This rock, like the preceding, is an old rhyolite (quartz por- 
phyry). The base is an olive-brown, fclty mass, holding opacito grains, 
quartz, feldspar, and decomposed black hornblende. Tiie characters of 
the quartz and feldspar are like those in the preceding rock. On the 
edges and in the cleavage planes of the feldspar, copper has been depos- 
ited in both of these rocks. No. 554, from the same locality, is a grayish- 
red, granitoid rock. In the thin section this is seen to be like the more 
granitoid trachyte pebbles found towards Torch Lake, and described 
before. This contains much secondary quartz, and a little that appears 
to bo primary. The feldspars are decomposed, and the quartz is so 
arranged in them that they show the graphic characters. The rock 
holds numerous rows of ferrite globules, which rows are arranged in a 
radiate form, giving to the slide a spherulitic appearance. A little of 
the feldspar is seen to be triclinic. No. 5G2 is a pretty brown rhyolite 
(felsite) with a very compact groundmass, holding some minute feld- 

feldspars are seen to be largely triclinic, while the groundmass is a 
brownish devitrified aggregate of secondary quartz, feldspar, and ferrite. 
The finer portions of the Calumet conglomerate arc seen microscopi- 
cally to be composed of the rhyolitic and trachytic detritus, the former 

* Bull. Mua. Comp. Zoology, V. 277-282. 

This was taken from the conglomerate of the Osceola mine. The 






predominating. In one of the enclosed fragments, quartz was seen 
containing several of the double pyramidal inclusions so common in the 
quartz of modern rhyolitcs. 

On the Mineral Point Railroad, abo4it three fourths of a mile from Han- 
cock, the melaphyrs were seen to be interbcdded with a number of con- 
glomerates. Certain pebbles intended to represent the different varieties 
"were collected. No. 419 is a very compact, fine-grained, reddish-brown 
rhyolitic rock (felsite). In the thin section it shows a compact ground- 
mass, made up of the devitrification products : quartz, feldspar, and ferrite. 
No. 420 has a reddish-brown groundmass, holding reddish feldspars and 
black hornblendes. The feldspar is seen in the thin section to be much 
decomposed, and part holds quartz in the graphic form in it. Some 
retains traces of its triclinic character, but all has the same hematite 
alteration' product that is common in orthoclase. The hornblende crys- 
tals of this old trachyte are changed to ferrite and viridite. Besides the 
quartz, ferrite, and viridite, as another alteration product cpidote occurs. 
This mineral is quite abundant. Magnetite and some apatite were seen. 
No. 421 has a very compact, reddish-brown felsitic groundmass, holding 
feldspar crystals. This old trachyte (feldspar porphyry, or felsite), in 
the thin section, is seen to have a reddish-brown groundmass, composed 
of alteration quartz, feldspar, and ferrite. The porphyritically enclosed 
feldspars are largely plagioclase. No. 422 is another trachyte (felsite 
porphyry), containing numerous reddish and greenish-gray feldspar crys- 

tals, held in a dark, reddish-brown groundmass. Microscopically the 


feldspars and groundmass are seen to be greatly decomposed and kaolin- 
ized. Viridite, epidote, opacite, and quartz occur as alteration products. 

This rock is closely allied to the andesites. 

No. 423 is a very fine-grained reddish granite, composed of feldspar, 
quartl, hornblende, and biotite. Considerable alteration quartz, fcriitc, 
and opacite were seen. The feldspars are much altered. The quartz 
contains fluid, vapor, and stone cavities, also numerous trichites. 

No. 424 is a brick-red granitoid trachyte (granite porphyry). The 
feldspar is much decomposed, and has the alteration quartz arranged in 
the graphic form. The rock shows through its alteration a somewhat 
spherulitic structure. This arises from the radiating arrangement of 
the alteration products in the groundmass. The sandstone found asso- 
ciated with the conglomerates is made up of the fine detritus of these 
trachytic and rhyolitic rocks, mixed to a greater or less extent with the 
basaltic materiah 

The sandstone and conglomei'ate west of the traps were studied in sev- 

■ ■■j-uvJ— J■-»VJ^^>Lv- rmj— r:ji.^->n ^— -|*^.-Ki 

ymiiii3itfci^»iz>**^.aw_^ofl-'i>r^ia2Kfc:^^^ ■-'lllI*^^|■SL^S1tSZlJ■^ 



eral places, especially at Copper Falls, west of Houghton, and northwest 
of Hancock. At the latter locality, marked slates on the map of the 
Portage Lake district, by A. K. Marvine and L. G. Emerson/^- or, in other 
words, at the bottom of the ravine below the curve, at the end of the 
heavy grade of the Mineral Range Railroad, they were examined the 
most thoroughly, as that locality seemed to be the most probable place 
to find fossils, if any existed in the sandstone. Although our search 
■was unsuccessful, we think it very probable that, if one had the appli- 
auces for more extended work, fossils might be found here. The con- 
tact of the sandstone with the traps was not seen here. In the parts 
nearest the latter it is a coarse, reddish-brown sandstone, composed of 
reddish feldspar, quartz, and basaltic detritus (387, 388, 409). It is 
composed of the same materials as the sandstone, interbedded with the 
basalts, although it perhaps has more basaltic detritus than they do. 
The enclosed pebbles appear to be trachyte (felsite porphyry), of the 
same character as those found within the trappcan district near Ilau- 
cock (3SD). 

As we recede from the traps, the sandstone becomes finer, or passes 
into a shale composed of the same materials (3D0, 3U1). Lenticular or 
rounded concretions occur in the shale, which closely resemble pebbles 
(392). Little spherical concretions of sand, similar to those described by 
Messrs. Foster and Whitney,! occur here (393, 394). In some of the 
coarser portions of the sandstone, interstratified with the shale, little 
fragments and scales of argillite were seen (395). Some of the shale 
is fine and earthy (398), and in places shows rain-drop impressions (399, 
400), ripple-marks (400, 401, 402), and mud-flows (403, 404, 405, 408)! 
About two miles above Hancock the sandstone was formerly quarried, 
on the shore of the hike. Its dip is N. 30^ W. 23^ The dip of the 
conglomerates nearer Hancock, interstratified with the traps, is 40°. 
Any inequality of the lava flows or of the shore deposits of sand and 
pebbles would give rise to a change in the dip of succeeding beds. 

West of Houghton, sandstone and conglomerate of the same general 
character was observed dipping N. 45° W. ,30°. It is probable that the 
Laumontite('*red Zeolitic mineral") which Dr. Rominger describes as 
occurring here, and also forming the cement of the conglomerates else- 
where, 1: is the red feldspar of the trachytes (felsitcs). The material of 
which the western sandstone is composed, and its junction with the 

* Gool. of Mich., I., Atlas, Plate XIV. a. 
t Kxecntive Docs., 1st Sess. ;Ust Cong., 18t9 
t Gcol. of Mich., I., Part HI. pp. D7, 93. 

I ^1 
I --T 


■l I 


50, IX., Doc, 69, p. 112. 



trap, all show that it is of the same geological age as the trappcati 
rocks, although joimger in point of time. 

The sandtstoncs and conglomerates are evidently beach-worn, and 
are simple shore deposits. Whence the trachytic and rhyolitic ma- 
terial came, is a subject worthy of future investigation. They were 
evidently lavas that had been erupted prior to the basaltic flows, and 
a knowledge of their original position, as well as tracing the ditferent 
kinds to their present resting-place, would give us considerable knowl- 
edge of the physical geography of that old sea. The conglomerates 
occurring interbedded with the traps would of necessity be more limited 
and variable than the lava flows themselves, for they could only be 
deposited upon the part of the lava that lay along the shore line, and 
even there only in those places where the conditions were favorable to 
the accumulation and retention of detritus. The amount of conglom- 
erate would in some measure depend upon the length of time elapsing 
between the basaltic flows; but on account of the local nature of the 
conglomerates, their absence at any particular spot does not prove the 
immediate following of the succeeding eruption, or that no conglomerate 
exists elsewhere between the two lavas. 

While we were able to do nothing to prove the geological age of the 
eastern sandstone, it seems that Dr. Eominger has brought forward 
evidence conclusively establishing the correctness of Messrs. Foster and 
Whitney's view, based on its stratigraphical relations, that it was of Pots- 
dam age. We have shown sufficient evidence to prove that in the parts 
visited by us the eastern sandstone conformably underlies the trap, and 
that, as held by Messrs. Foster and Whitney, the eastern and western 
sandstones, and the traps lying between them, are of the same geologi- 
cal age. Whether the idea is correct or not, as held by these gentle- 
men, that the eastern sandstone at the Bohemian and Porcupine Moun- 
tains is younger in order of time of deposition than the traps, and was 
originally continuous with the western sandstone, we cannot say, having 
never studied the sandstone in either locality. It is, however, plain that 
Buch is not the relation of the eastern sandstone in the vicinity of 
Torch Lake to either the traps or western sandstone. It is also evident 
that the volcanic action began gradually the same as it ended, and pro- 
duced similar alternations of trap and sandstone on both sidcti of Ke- 
weenaw Point. 




The Veins and Copper Deposits. 

At some time after the sandstones, conglomGratcs, and traps were 
laid down, extensive and deep-seated fissures were formed, generally 
extending, in the distriet north of Portage Lake, aerosa the beds. These 
fissures seem to have been formed by powerful movements of diflerent 
parts of the roeks, causing their cross fracture and dislocation. The 
movements have been repeated from time to time, causing a rubbin'^- 
grinding, breaking, and polishing of the parts adjacent to the fissures, 
forming numerous slickensides. These movements would not cause ir- 
regular and secondary fracturing to any great extent after the main fis- 
sures had been formed, in the heavy-bedded diabases or the sandstones • 
but in the seoriaceous and thin-bedded melaphyrs, the tendency to yield 
to the pressure was much greater, and the rock adjacent to the fissures 
was broken up to a considerable extent. During the time of the fractur- 
ing, and since, the fissures served as channels for water. In the seori- 
aceous and easily decomposable melaphyrs the water served by its 
decomposition of the adjacent rock to widen the fissures, but in the 
diabases, although their composition was the same, their structure and 
the absence of much glass prevented the same results occurring. The 
sandstones and conglomerates, from their being principally composed 
of trachytic and rhyolitic material, and from their structure, suffered 
little, compared with the melaphyrs, from vein formation. 

In many localities the evidence is strong that the percolating waters 
were hot- in others, as remarked by Marvine, no sign exists that it was 
above the temperature of the present day. AVater penetrated with 
greater or less readiness through the traps themselves, causing their de- 
cay and alteration, while the substances taken up in solution by it were 
deposited in the fissures, cells, and other open spaces in the rock. The 
filling of pre-existing cavities and fissures gave rise to the amygdaloidal 
structure of the traps and the vein material ; the decomposition of the 
trap, and its replacement of some materials by others, gave rise to 
the pseudo-amygdaloidal structure. This structure exists not only in 
the non-scoriaceous or non-cellular portions, but also in the truly seori- 
aceous or cellular portions. 

All or nearly all of the material filling the veins and adjacent traps 
appears to have been derived from the decomposition of the traps them- 
selves, and not brought in from extraneous sources, — this decomposition 
being brought about by the medium of the percolating waters, whoso 
course seems, in many cases at least, to have ^ccn downwards. The par- 




tial decomposition of the fractured portions of the traps and the filhiig 
of the interspaces by the vein matter give rise to the great width which 
the veins sometimes attain, - thirty feet. While the veins in the nar- 
rower portions are often filled with pure vein material, in the wider 
parts they are composed of a breccia of decomposed trap cemented by 
vein matter. The comby and sheet structure of the veins, the class of 
minerals enclosed, the decomposition of the associated melaphyr, — in 
fact, all their characters, — point out that these are true fissure veins 

filled by segregation. 

In the veins the copper is found intimately mixed with the gangue, 
or in sheets or irregular masses. The copper in the sheet form, as 
is much of the mass copper of the veins, extends downwards, or has 
its sides an)roximately parallel with the walls of the vein. Oftentimes 
the sheet bifurcates, holding some of the gangue or melaphyr between 
its parts (818). On cutting the mass copper it is not uncommon to find 
completely enclosed in it masses of melaphyr, (piartz, calcite, or other 
of the vein materials. The association, structure, and the relations of 
the copper to the vein material and to the traps, all show that it was 
deposited in the same way the vein matter and secondary materials iu 

the traps were. 

The mclaphyrs adjacent to the veins arc often impregnated, in the 
decomposed portions, with copper, as well us the usual secondary de- 
posits. In certain cases it has paid to take out the parts adjacent 
to the vein, but fallacious have proved and will prove the hopes of 
continous profitable mining based on these local deposits. Vein mines 
associated with local deposition of copper in the adjacent traps have 
been and are now so abundant at Lake Superior that it would be invidi- 
ous for us to specify any one of them. In the vicinity of Portage Lid.e 
the old lava flows themselves arc mined. No trace or sign of a true 
fissure vein exists in most of the beds that are mined in this locality. 
The miuin- is confined to work upon unstratified deposits, the same as 
if some of the more cellular and deeply buried lavas of Vesuvius or 
■ Etna were for any reason mined. These mclaphyrs have been gi'eatly 
acted upon by hot waters, which have decomposed them, an.l deposited 
the copper in an irregular, " bunchy " maimer. On the Isle Uoyale lode 
this hot-water action is very strongly markc.l, the original basalt being 
now greatly altered, and filled with epldote and .piartz, or other min- 
erals (377, 378, 379, 380, 381, 382, 383, 384). 

In others the action is not so strongly marked, but more evenly dis- 
tributed throughout the bed, as for instance the Quiiu'v. All these bed 






mines have their deposits distributed iu a very irrcgnlar manner, requir- 
ing much dead work as a neccessary concomitant of the way in which 
the copper was deposited. 

Another variety of the bed mining is that known as ash-hed mining. 
As stated before, the ash-bed is a more scoriaceous flow than the iiener- 
ahty of the mehaphyrs to which it belongs, and has the copper deposited 
throughout its mass, not rich, but quite uniform, or subject to certain 
wclbmarked hiws of variation. So far as could be ascertained, the ash- 
bed shows no sign of hot-water action at Copper Falls, but rather 
evidence that the copper was deposited from a cold, or, at most, only 
a warm solution. The rock is but little changed, and retains part of 
the signs of its fluid state, almost as well marked as they are in some 
comparatively recent lavas. Iu other mines iu which a transverse fissure 
vein and a melaphyr (amygdaloid) is mined, the impregnation of the 
melaphyr with copper seems to be dependent upon its proximity to the 
vein, being rich near the vein, but growing poorer as it recedes from 
it. Here the conditions are reversed : the ashd)ed is apt to be poorer 
near tlio veins than at a distance from them. Where the overlying 
trap sent down tongues into the ash-bed, the latter became indurated, 
and consu(piently but little copper was deposited in it at these places. 

The Atlantic mine at Portage Lake is supposed to bo on the ash-bod, 
or a similar formation. This mine was visited, and the rock found to 
be similar to that of the ash-bed, except much harder. This rock has, 
like the rock in the other mines at Portage Lake, been subjected to 
much more intense metamorphic action than the ash-bed at Copper Falls. 
The copper here, however, is quite evenly distributed, and all of tlie bed 
is stoped out and sent to the stamp-mill. So far as could be told by 
lithological evidence, the Atlantic mine is on tlie same bed as the Cop- 
per Falls mine, or on a bed having the same origin. The action of 

thermal waters on the former accounts for its present diflxirence from 
the latter. 

The induration of any rock does not apparently depend upon the 
question of the heat of the water which acts upon it, but upon the depo- 
sition of mineral matter in the rock by the water, and on the hardness 
of the deposited minerals. No mineral matter need be brought in; the 
induration requires only that the chemical constituents should rcimitc 
into minerals of greater hardness. These alterations arc always a pas- 
sage from unstable to more stable compounds, in tlie conditions to which 
the rocks are subjected. Glass is the most unstable form in which any 
of the rock constituents can be; but the uielaphyrs, from their origin 



and the conditions to which they were subjected at the time of con- 
solidation, must have possessed a vast amount of glassy material. 
Hence they were most liable to decomposition and alterationj which 
might or might not result in induration. At Copper Fails no general 
induration exists, except, for instance, where quartz has been deposited, 
but at the Atlantic the induration is general. We have seen, tliat the 
action of hot waters on the sandstone at Torch Lake gave rise to the 
reverse of induration, as its action was that of removal, and not of 


The last form of copper deposit in the district visited by ns is that 
of the conglomerate mines. The beds of conglomerate are composed, 
as before said, of rhyolitic, trachytic, and basaltic pebbles and detritus. 
In some of these conglomerates, as the Calumet and Ilccla, the cement 
has been removed, and its place, or the original interspaces, filled with 
copper. In some cases mclaphyr pebbles have been largely removed, 
and their places filled with copper, giving rise to boulderdike forms 
(471). These conglomerates, then, are simply old sea-beach deposits, 
and, like the amygdaloids and ash-beds, are not veins, and cannot prop- 
erly be so called. They must of necessity partake of the characteristics 
of their origin, the same as veins do of theirs. 

The copper has been found throughout the district underlying heavy 
beds of trap or a series of smaller ones; in fact, in the parts visited by 
us, experience has shown that copper in abundance was only found 
■where trap in large amounts overlaid the vein or bed. The copper was 
found filling, at the Calumet and Hecla mine, the joints of the overly- 
ing trap, and extending as a continuous sheet through fissures at right 
angles to one another. At Copper Falls spikes of copper extend down- 
wards out of the overhanging trap into the ash-bed. Tliese are generally 
large at the upper end, and pointed at the lower. Like them are the 
secondary depositions of calcite, in this trap, in long, spike-like forms, 
that here and elsewhere have been taken for fossils. These features 
prove that the copper came from above downwards, and that it was de- 
posited after the jointing of the trap. In fact, the evidence is strong 
that all the alteration and Assuring of the rocks, and the deposition of 
the copper and associated minerals, took place after the western sand- 
stone had been deposited. The above facts indicate that the copper was 
derived from finely disseminated copper distributed throughout the lava, 
as modern lavas have been known to contain it. If it was derived from 
the sandstone, as advocated by Bauerman and later by Pumpelly, it 
should be found in connection with the sandstone; but such is not the 



case. The farther from tlic sandstone, and the nearer the heavy beds of 
trap, the larger have been the deposits of copper, e. g. Chff, Central, and 
Calumet and Heela. The conglomerate of this last mine was not the 
home of the copper ; it is simply the place where it has been deposited 
by secondary agencies. The statement now kept up for some thirty 
years in Dr. Dana's works, that the copper is chiefly found at the junc- 
tion of the sandstone and trap, is a good illustration of how an error once 
m a text-book cannot be eradicated. 


The general geological structure of the region visited by ns is, then, 
in general, as follows. Beginning on the southeastern side of Keweenaw 
Point we find a sandstone and conglomerate overlaid by melaphyr. 
This melaphyr is again overlaid by sandstones and conglomerates^ 
principally the latter. The alternations of melaphyr, diabase, sandstone, 
and conglomerate, with the melaphyr and diabase largely predominat- 
ing, continue across the centre of the Point, forming its backbone. As 
the northwestern side is approached, the sandstones and conglomerates 
increase, while the melaphyr and diabase diminish, until a purely sand- 
stone formation is reached. 

All these rocks taken together make one geological formation, and 
have been laid down successively one upon the other, in order, going 
from the east towards the west. These rocks arc known to form the 
same series by their conformably overlying one anotlier. These traps 
are old lava flows, spread out over the then existing sui'face along 
a shore line. They have flowed the same as modern basaltic lavas do 
imder like conditions, and retain the same characters, except* so far as 
thoy have been modified by the agencies to which they have been sub- 
jected since their outflow. They are known to be old lava flows by their 
baking and indurating the immediately underlying rock, by their send- 
ing dikes and tongues down into this rock, by tlieir scoriaceous charac- 
ter on the upper surface, by their signs of having flowed, and by their 
microscopic characters. That they were laid down before the over- 
lying rock is shown by their producing no effect upon it ; by their 
presenting on the upper surface only the irregularities and rounded 
knobs that such surfaces are known to have, especially when they have 
been worn ; by rounded pebbles and boulders of the underlying traps, 
being enclosed in the overlying conglomerates ; by the absence of frag- 
ments of the overlying rock iu the underlying one; and by the ab- 




scnce of any characters showing intrusion of the traps between the dif- 
ferent beds. The extent of these old lava flows, excej^t as seen along 
their upturned edges, is not known, for they have been followed by 
mining along their hicline some 2,100 feet only. Judging from their 
length, their width must be considerable. In thickness they partake 
of the same irregularities which any similar flow has. Locally the thin- 
ner and more scoriaceous flows are known as " amygdaloids,^' the thicker 
and more compact ones as *' traps," and the thickest one on the western 
side as "greenstone." The difierence between these several forms of 
old basalt seems to be occasioned only by the variable amount of lava 
erupted at different times, and the slightly dilTerent conditions to which 

the flows were subjected. 

Most of these old basalts are directly covered by succeeding flows, 
followung after greater or lesser intervals of time ; but part, as remarked 
above, are covered by conglomerates and sandstones. These conglom- 
erates and sandstones show, by the rounded and water-worn character 
of their constituent pebbles and grains, that they are beach deposits. 
The surface of the underlying basalt is smoothed as by water action. 
The overlying conglomerate is made up at its base of })asaltic mud and 
pebbles, derived from the underlying rock, and mixed with the felsitic 
mud and pebbles of which the conglomerates are chiefly composed. The 
trappean mud and pebbles diminish, or are entirely wanting, as wc re- 
cede from the underlying trap. That the basalt is a metamorphosed 
sandstone, as is often contended by mining men, is disproved by the facts 
given above, and by the further facts, that there is no gradual, but an 
abrupt, passage between the two ; that all fi'agments of sandstone caught 
up by the trap are baked and indurated by the heat, but show no signs 
of passage; and, lastly, that it would demand the conversion of an acidic 

rock into a basic one. 

From the conditions given above it would not be surprising to find the 
lava flows locally limited at any point, and partially or even entirely de- 
nuded, and replaced, in part or as a whole, by conglomerates and sand- 
stones. This would depend, of course, upon the position of the shore 
line, and upon the conditions to which the basalt was subjected during 
the time of its flow, or since. A still greater variability is to be looked 
for in the conglomerates and sandstones. All these conditions are to be 
taken into consideration in the mining of these old lava flows and their 

associated conglomerates. 

In the Portage Lake and Keweenaw Point districts there are mined at 

present four forms of deposits: 




1. Mclaphyrs of an aniygdaloidal character, known as "amygdaloid" 
mines, which have been subjected to hot-water action, and whose depos- 
its of copper are '' bunchy " and irrcguLir. These are in no sense veins 
or lodes, and the Qiiincy and the Sheldon and Columbian mines are 

good examples. 

2. Ash-bed. mines, which are truly melaphyr or *' amygdaloid" ones, 
but the melaphyr is of a more scoriaccous character, as was pointed 
out above, of which the Copper Falls (in part) and the Atlantic mines 

arc examples. 

3. The conglomerate or true bed mines, hke the Calumet and llecla. 

4. The true fissure vein mines, iike the Central, Phcenix, and Copper 
Falls (in part). 

The first two forms should be classed as one. 

It is an established rule that a mineral vein, in passing from one bed 
of rock into another of a different nature, is apt to vary in width and con- 
tents. Such variations in dimensions and gangue have been repeatedly 
found in this district, as the different beds arc comparatively narrow. 
As might be expected, the variation is not so strongly marked in the 
dillerent mclaphyrs, since they are all rocks of the same composition and 
origin, dillering only in texture, thickness, and crystallization. One and 
the same vein may then vary in width, from a mere scam to thirty or 
more foot, as is the case with the "Owd Creek Vein," as mined at Cop- 
per Falls. Under tliesc conditions one cannot judge with any certainty, 
from the appearance of tlio vein at one point, what will be its width or 
character at another. The decision must be based on probabilities only. 
In places the fissure may be filled with true vein matei'ial, while in other 
parts, especially in the wider portions, it may be filled with fragments 
of the melivphyr, cemented together by vein matter. The width of the 
vein will depend largely upon the readiness with wdiich the country rock 
yielded to the crushing and grinding force, and to the action of the per- 
colating waters. We should expect, then, the veins to be mere nominal 
fissures in the sandstones, conglomerates, and heavy "greenstone," but 
to be more or less well marked in the "amygdaloids " and "traps." 

The filling of the veins and of tlie cavities in the melaphyi's, it ap- 
pears, was accomplished by the same agencies. The amygdaloidal struc- 
ture of the melapliyr is owing to the filling with mineral matter, with 
^a-eater or less completeness, ga.s cavities formed at the time of the lava 
flow. Besides the true amygdaloidal structure, there arc numerous 
cases of pseudo-amygdaloidal structure. I'liis last arises from the alter- 
ation of the formerly solid parts of the melaphyr, and is to be found not 

VOL. VII. — KO. 1. 9 



only in the compact portions (lower) of the rock, but also in the scoria- 
ceous parts (upper). These amygdules and pscudo-aniygdules are com- 
posed of quartz, calcite, epidotc,prehnite,Iaumoutitc, analcite, apophyllite, 
datolite, cidortte, delessite, etc., etc. The constituents of these minerals 
were derived from the decomposition of the melaphyr, and deposited 
through the agency of the percolating waters. The vein materials are 
the same as those of the amygdules, and they are of like derivation and 
deposition. The copper is found forming a constituent part o( the amyg- 
dules in many places, as well as of the vein-stone, and it would seem to 
have been deposited in a like manner. Until we know more about the 
occurrence of the copper, all theories regarding its origin should be held 
with a loose grasp, and dropped as the facts developed may require 
thereafter. It is held by some that the copper was derived from solu- 
tions of the metal in sea-water, precipitated by decaying organic matter, 
and accumulated in the sandstones, shales, and conglomerates of the 
series. It was then taken up by the percolating waters, and deposited 
in the places in which it is now found. A second view is that the cop- 
per was originally finely disseminated through the lava at the time of its 
outflow, and has since been locally concentrated by percolating waters 
in the amygdules, veins, and conglomerate beds. The writer inclines to 

the latter view, believing that this theory is more in accordance with 
the facts observed by him than the former one. The final concentra- 
tion and precipitation seem to be connected in some way with the ox- 
ides of iron, which are abundant in the melaphyr and in the detritus of 
it and of the felsite pebbles, which form the principal portion of the con- 
glomerate. The copper seems to have needed for its deposition some of 
the following conditions: rocks that were porous and cellular; those 
whose parts were easily removed by the percolating waters, as the mud 
forming the cementing material of the conglomerates; the open spaces of 
veins and fissures ; and rocks acted upon by hot waters. TIxq coj)per, 
when not distributed through the whole bed, is found principally in the 
upper portion. Whatever may be our views respecting the sources of 
the copper, it is evident that it was deposited by aqueous agencies, and 
that the general course of the solution was downwards. The best vein- 
stones, so far as observed, are datolite, prehnite, and caleite. Laumon- 
tite does not seem to have much mass copper associated with it. While 
large masses of copper were seen at the Central mine associated with 
caleite, a similar association is I'arely found in the Owl Creek vein at 
Copper Falls. The best vein-stone there has been datolite. The preh- 
nite here seems in depth to yield to datolite. 



The theories of the igneous origin of the veins, and of the igneous 
deposition of the copper in them, have hecn so ably refuted in the vari- 
ous papers referred to here that it is unnecessary to discuss them ; but 
owing to the great weight of Professor Dana's name, we cannot pass 
over his theory without saying that the supposed facts on which it is 
based do not exist in the Copper district, he having raised the super- 
structure on the errors of Messrs. Houghton and Jackson, never having 
visited the region himself. 

As in the Iron district, so in the Copper district, the writings of 
Messrs. Foster and Whitney ren:iain the best and most accurate expo- 
nents, as they were the first of value, of the geology of the country, and 
of the ore deposits studied by us, so far as they were known at that time. 
All work since, so far as it stands the test of examination, sustains their 
views and establishes the accuracy of their observations, except in a few 
particulars. Mr. A. K. Marvinc's work stands next in order of value 
and geological ability shown. 

Professor Pumpelly deserves all credit for his microscopic examina- 
tions of the old basaltic rocks of the district, and for the extent and 
thoroughness with which he has applied and carried out the investiga- 
tions and theories of Messrs. Whitney, Miiller, and Bauerman, in his 
*' Paragenesis and Derivation of Copper and its Associates on Ke\veenaw 
Point " ; but his stratigraphical work was not worthy of the name, and 
served only to obscure the true relations of the rocks. The volcanic 
origin of the rocks was proved by Marvine five years before, by Foster 
and AVhitney twenty-eight years before, and announced by Hubbard 
thirty-two years before Pumpelly accepted it. 

Our work proves that the Keweenawan system has no foundation 
except in insufficient observation and the application of stratigraphi- 
cal methods and assumptions that will not bear examination. The 
difficulty here, as in the Iron district, has been in t!ie methods, and 

in the assumption that certain observations proved that which they 
did not. 


I desire to extend my thanks for favors received while in the Iron and 
Copper districts to Charles E. Wright, M. E., State Commissioner of Min- 
eral Statistics; Per Larson, M. E. of the Jackson mine; Agents C. H. Hall, 
of the Lake Superior mine, William Sedgwick, of the Baruum, D. H. 
Bacon, of the McCombor ; Capts. James Pascoe, of the Champion, and 
Peter Pascoe, of tlic Republic ; also to Mr. David Morgan, President of, 
the Republic Iron Company; to Captain Cliff, and L. G. Emerson^ M. E. 




of the Quiiicy ; Messrs. Cooper and Patch, of tlie Detroit and Portage 
Lake smclting-works ; G. D. Bolton, M. E., and Capts. Iloatson, Dan- 
iel, and Wells, of the Cakunet and Hecla; Mr. Frank Osburn, of the 
Troy Polytechnic School ; Agent Delano, of the Phoenix ; and espe- 
cially to Agent B. F. Emerson and Captain John H. Moyle, of the 
Copper Falls mine ; and others. 


Cambriuge, Mass., May 18tli, 1880. 







List of Papers and Works relating to the Geology, Mineralogy, and Physi- 
cal Geo<p-aphy of Lalce Superior, 

The writer docs not claim that thi« list contains all that has been 
written on these subjects relating to Lake Superior, for it is simply the 
outgrowth of a desire, arising after part of the body of this paper was 
written, to save others the trouble of doing over again the work that ho 
had already done. It is not intended as a bibliography in the approved 
modern sense, but simply to serve as a stepping-stone to those who may 
hereafter desire to take up the study of this most interesting region. 
Piipcrs and works, wliicli from their titles appear to belong to diflercnt 
departments or to other localities, have been given, when matter re- 
lating to these subjects or this region, as the case may be, has been 
found in them. All papers given here that the writer has not seen are 
marked with an asterisk (*). 

In the preceding text, in quoting from the various authors referred to, 
the intention has been to nudie the spelling, punctuation, and italics 
identical with the originalSj which accounts for certain peculiarities that 
the reader will observe. 


Agassiz, Alexander. 

Oa Uic Posit.iou of the Sandstone of tlie Sontlicrn Slope of a PoHion of 

Kcweeniiw roiuij Lake Superior. Proc. Bost. Soc. Nat. Hist., 18G7, xi. 

Agassiz, Louis. 

Ou iJic Piylics of LalvC Superior. Proc. Am. Assoc. Adv. Sci., 1848, i. 

The Terraces and Ancient llivcr Pars, Drift, Boulders, and Polislicd Siu'- 

faccs of Lake Superior. Proc. Ani. Assoc. Adv. Sei., 1818, I. G8 -70. 
Oa tlic Origin of the ActAud Outlines of Luke Superior. Proc. Am. Assoc. 

Adv. Sei., 1848, i. 79. 
Remarks upon the Unconformablllty of tlic Pakienzoic Pormations of the 

United Stales. Proc. Am. Assoc. Adv. Sei., 1851, vi. 254. 
On Mareou's "Geology of North America." Am. Jour. Sei., 1859, (2,) 

xxvii. 134-137. 



Agassiz, Louis, and J. Elliot Cabot. 

Lake Superior. Its Pli^'sical Characters, Vegetation, ana Animals. Boston, 
March, 1850. 428 pp. Edinburgh New Phil. Jour., 1850, (3,) xiix 25 
-33, 398, 399; Am. Jour. Sci., 1850, (2,) x. 83-101, 
Akermann, H. W. 

Die Kupferlulirenden Scliichicn am Lake Superior. Sitzungs-Berichtc dcr 
naturwisscusehafllicbcn Gcsellschaft Isis in Dresden, 1875, pp. 101-105. 
Alger, Francis. 

Pseudomorphic Crystal of Native Copper from Copper Palls Mine, Lake Su- 
perior. Proc. Bost. Soc. Nat. Hist., 1861, viii. 170, 171. 
Andrews, Israel D. 

On the Trade and Commerce of the British North American Colonies, and 
upon the Trade of the Great Lakes and llivers. Sen. Docs., 1st Sess. 32d 
Cong., 1851-52, xi.. No. 112, 90G pp. Contains a report by C. T. 


Michigan : its Commerce and Bcsourees. Hunt's Mercli. Mag., 1843, vi. 

The Copper Mines of Lake Superior. Hunt's Merch. Mag., 184G, xiv, 439- 

Anciciit Mining on Lake Superior. Hunt's Merch. Mag., 1848, xix. 0G3. 
Elevation of an Island in Lake Superior. Ann. of Sei. Discov., 1851, 255. 


The Copper and Iron Begion of Lake Superior. Review of the Work of 

P. C. L. Koeli. Mining Mag., New York, 1853, (I,) 201 -208. 
The Silver of the Lake Superior Mineral Region. Mining Mag., New York, 

1853, (1,) i. 447-454, 012, 013 ; ii. 82, 83. 
Notice of a Geological Map of the United States, etc., by Jules Marcou. Am. 

Jour. Sci., 1854, (2,) xvii. 199-200. 
Mineral Wealth of the Lake Superior District. Ann. of Sei. Disc. 1855, 

309, 310. 
Mineral Region of Lake Superior. Mining Mag., 1858, (1,) ii. 248-252. 
Great Mass of Native Copper. Min. and Smelt. Mag., 1804, vi. 25, 20; Am. 

Jour. Sci., 1804, (2,) xxxvii. 431. 
Canada. A Geographical, Agricultural, and Mineralogieal Sketch. Published 

by authority of the Bureau of Agriculture. Quebec, 1805, 33 pp. 
Barnes, George O. 

See Charles T. Jackson. 

Bartlit, William, and David Tod. 

Mineral Regions of Lake Superior. Senate Docs., 1st Scss. 29lh Cong., 

1845 - 40, iv.. No. 100, pp. 20 - 25. 
Bayfield, H. W. 

Outlines of the Geology of Lake Superior. Trans, of the Lit. and Hist. Soc. 
of Quebec, 1829, i. 1-43. 

On tlie Junction of the Transition and Primary Rocks of Canada an3 Labra- 
dor. Quart. Jour. Gcol. Soc, 1845, L 450-459. 



Beaumont, Elie de. 

Age of ihe Saudsioiic of Lake Superior. Bull. Soc. Gcol. France, 1819 - 50, 
(3,) vii. 209. 

See Louis Cordier. 
Bell, Robert. 

Geology of Lake Superior aud Nipigon. Gcol. of Canada, 1SG6 - G9, pp. 

lloport on the Country ^^orth of Lake Superior, behvcen the Nipigon and 
Micliipicotcn Rivers. Gcol. Surv. of Canada, Rep. of Prog., Ottawa, 

1870-71, pp. 322-351. 

Report on the Country between Lake Superior and the Albany River. Geol. 
Surv. of Canada, Rep. of Prog., Montreal, 1871-72, pp. 100-114. 

Report on the Connti-y between Lake Superior and Lake Winipcg. Geol. 
Surv. of Canada, Rep. of Prog., Montreal, 1872-73, pp. 87-111. 

The Mineral Region of Lake Superior. Canadian Nat. and Gcol., 1875, (2,) 
vii. 49-51. 

Report on an Exploration in 1875, between James Bay and Lakes Superior and 
Huron, Gcol. Surv. of Canada, Rep. of Prog., 1875-70, pp. 291 - 312. 

Report on Gcologieal Researches North of Lake Huron and East of Lake Su- 
perior, Geol. Survey of Canada, Rep. of Prog., 1876-77, pp. 193-220. 

Bell, William H. 

Mineral Lauds of the Upper Mississippi. Executive Docs., 1st Sess. 2Sth 

Cong., 1813-44, iii., No. 43, 52 pp. 

Bigsby, John J. 

A List of Minerals and Organic Renuxins occurring in the Canadas. Am. 

Jour. Sci., 1824,(1,) viii^ 00-88. 
Notes on the Geography and Geology of Lake Superior. Quart. Jour. Sci. 

and Arts, 1821-25,''xviii. 1 -34," 228 -209. 
On the Erratics of Canada. Quart. Jour. Geol. See., 1851, vii. 215-238, 

with map. 
On the Physical Geograpliy, Geology, and Commercial Resources of Lake 

Superior. Edinburgli New Phil. Jour., 1852, liii. 55-02; Am. Jour. 

Sci., 1852, (2,) xiv. 138 ; Proe. of the Royal Institution, 1852, i. 151-102. 
On the Organic Contents of the Older Mctamorphic Rocks: a Review and a 

Classification. Edinburgh New Pliil. Jour., 1803, (2,) xvii. 171 - 197. 

Billings, E. 

General Geology. Canadian Nat. and Gcol., 1850, i. 1 -25. 

Blake, William P. 

Review of a Portion of the Geological Map of United States and British 

Provinces, by Jules Mar'-ou. Am. Jour. Sci., 1S50, (2,) xxii. 383-388. 

The Mass Copper of Lake Superior Mines and the Metliod of Mining it. 

Trans. Am. List. Min. Engineers, 1875, iv. 110-112. 

Blandy, John F. 

Topography with especial Reference to the Lake Superior Copper District. 
Trans. Ani. inst. Min. Engineers, 1871, i. 75-82. 


... ._>-^-Mn^x 



Stamp Mills of Lake Superior. Trans. Am. Tnst. Mhi. Eng., 1^7^, ii 

Tlic Lake Superior Copper Rocks iti Pennsylvania. Trans. Am. Tnst. Min. 

Eng., 1879, vii. 33i-3;3;3, 3:30. 
>SV C. p. Williams. 

Borie, Jules. 

* JS'oLiee sur Ic Lac Superieur ct scs Mines do Cuivrc do la Hive Amcricaine. 
St. Etieuue Bull. Soc. ludusir., 1800, vk 233-284; vii. 185-252; viii. 
271, 272; Ailgem. Berg. u. llilttcn. Zeituug, 18G2, iv. 118-450, 457- 
4G0, 4i)'J-47i. 

Bradley, Frank H. 

Ou a Geological Chart of tlic United States east of the Uoeky Mountains, and 

of Canada. Am. Jour. Sek, 1870, (3,) xIL 280 -291. 

Bristol, T. W. 

iScc Jacob Houghton, Jr. 

Brooks, T. B. 

Geological Survey of Michigan, with Maps, 1809-1873, i. ; Part L, Iron- 
bcaruig Rocks, 319 pp.; Part IL, Copper-bearing Hocks, 11. Pumpeily 
and A. \i. Marvine, 143 pp.; Part 111., Palasozolc Rocks, Charles Rom- 
iiiger, 105 pp ; ii. 208 pp,, contains papers by Messrs. Brooks, Julicn, 
Wri'-'ht, Jeuncv, and Tuttle. 

On the youngest lluronian Rocks south of Lake Superior and the Age of Hie 
Copper-b('ariiig Scries. Am. Jour. Sci., 1870, (3,) xi. 200 -211. 

Classified List of Rocks observed in iJie lluronian Series, south of Lake Su- 
perior, etc. Am. Jour. ScI., 1870, (3,) xii. 194-204. 

jSre T. C. (Jhamberhun. 

Brooks, T. B., ajul R. Pumpeily. 

Ou the Ago of the Copper-bearing Rocks of Lake Superior. Am. Jour. Sci., 

1872/(3,) iii. 428-432. 

Brown, A. J. 

The Formation of Fissures 'and the Origin of their Mineral Contents. Trans. 

Am. Inst. Min. Eng., 1874, ii. 215 - 219. 

Burt, William A., and Bela Hubbard. 

Reports of William A. Burt and IJela llubljard on the Geography, Topogra- 
phy, and Geology of t,he U. S. Surveys of the Mineral Region of the South 
Shore of Lake Superior for 1845, etc. In the "Mineral Region of Lnke 
Superior," by -L Tlf)ughtoii, Jr., and T. W. Bristol. Detroit, 1840. Sen- 
ate Docs., 1st Sess. 29lli Cong., 1815-40, vii. Doc. 357, 29 [)p. ; 1st 
Sess. 31st Cong., 1849-50, iii. 803-842. 

Geology and Topography of tin; District south of Lake Superior, 184G. Sen- 
ate Docs., 1st Sess. 31si Cong., 1849-50, Iii. 842-932. 

See Charles T. Jackson, aud Jacob 41oughton, Jr. 

Cabot, J. Elliot. 

/See Louis Agassiz, 




Callender, John A. 

The Lake Superior Copper Mines. Mitiing Ma^., 1854, ii. 249-253. 

Calvert, John. 

On the Dccomposiiiou of llocks and the Tlecompositioii of their Metallic Con- 
stituents. Mining Mag., 1851, iii. 371 "3?G. 
Campbell, J. B. 
^ee John Stoekton. 

Cass, Lewis. 

Letter from Governor Cass, of Michigan, on the Advantage of Purchasing 
the Country upon Lake Superior where Copper has been found. Senate 
Does., 2d Sess. 18th Cong., 1824-25, No. ID, 2 pp. 

Chamberlain, T. C. 

Geology of Wisconsin, 1873-1877, XL. 7GS pp. with maps. Reports by 
Messrs. I. A. Lapliam, O. W. Wight, T. C. Chamberlain, H. D. Irving, 
C. E. Wriglit, and Moses Strong. 1873-1879, III., 763 pp. with nuips. 
Reports by Messrs. E. D. Irving, E. Pun)pclly, A. A. Julien, C. E. 
Wright, E. T. Sweet, T. E. Erooks, A, Wiclunan.n, T. C. Cliauiberlain, 
and T. S. Hunt. 

Channing, William T. 

See Charles T. Jackson. 

Chapman, E. J. 

Po])ular Exposition of the Minerals and Geology of Canada. Canadian Jour., 
18G0, (2,) V. 1-19, 1GS-1S2, 517-531; 1801, vi. 140-105, 425-455, 

500-518; 1802, vii. 108-121; 1803, viii. 17- 33, 111 - 127, 185 - 210 
437-403; 1804, ix. 1-10. 

On Some Minerals from Lake Superior. Canadian Jour., 1805, (2,) x. 400- 

On Some Minerals from Lake Superior. Plnl. Mag., 1860, (4 ) xxxi 170- 

Notes on the Silver Locations of Thunder Eay. Canadian Jour 1869 (2 ) 


An Outline of the Geology of Ontario, based on a Sul)division of the Province 
into six Natural Districts. Canadian Jour., 1875, (2,) 580- 588. 

On the Loading Geological Areas of Cariada. Canadian Jour., 1876, (2,) xv 

Chester, Albert H. 

On the Percentage of Iron in Certain Ores. Trans. Am. Inst. Min. En"-. 
1875, iv. 219. 

Clarke, Robert D, 

Notes from the Copper 
433-448, 577-588. 



Harper's New Monthly Mag., 1853, vi. 

Clarke, T. C. 

The Great Lakes. Atlantic Monthly, 1861, vii. 220-235, 



Claypole, E. W. 

Ou the Pre-Glacial Geography of the Eegion of the Great Lakes. Canadian 

Kat. and Geol, 1878, (3,) viii. 187-206. 
Pre-Glai .'I Eormation of the Beds of the Great American Lakes. Canadian 
Na!. and GcoL, 1879, ix. 313-227. 

Clinton, De Witt. 

On Certain Plicnomena of the Great Lakes of America. Trans. Now York 

Lit. and Phil. Soe., ii., Part I. 1-33. 

Cordier, Louis. 

Note snr unc Masse de Cuivrc natif provenantdes Hives du Lae Suporieur, aiix 

iltats-Unis d'Amerique. Louis Cordier and Eliede Beaumont. Comptes 
Eendus, 1819, xxviii. 161-163; Leonhard's Jahrbuch, 1819, p. 470. 

Courtis, W. M. 

The North Shore of Lake Superior as a Mineral-bearing District. Trans. 

Am. Inst. Min. Eng., 1877, v. 473-487. 

Credner, Hermann. 

Die GUederniig der eozoisehcn (vorsilurisehen) Eormationsgrnppe Nord- 

Amerikas. Zoits. Gesam. Naturwiss., Giebcl, 1SG8, xxxii. 353-405. 

Bcschreiburig einiger charaktcrisiischer Vorkomnien dcs gediegenen Kupfers 
auf Keweenaw Point am Oberens See Nord-Amerika'i Leonhard's Jahr- 
buch, 1869, 1-14. 

Die vorsihirischen Gebilde der " Obern Halblnsel von Michigan" in Nord- 

Amerika. Zeit. Dent. Geol Gesell., 1869, xxi. 516-554. 
Gewaltige Kupfermassen am Lake Superior. Leonhard's Jahrbuch, 1870, 86. 
Leber nordamerikanische Schieferporphjroide. Leonhard's Jahrbuch, 1870, 

Elemcnte der Geologic. *lst ed. 1872, *2d ed. 1872, 3d ed. 1876, 699 pp., 

^4thcd. 1380. 

Crosby, William O. 

On a Possible Origin of Petrosillceous Eocks. Proc. Bost. Soc. Nat. Hist., 

1879, XX. 160-169. 
Contributions to the Geology of Eastern Massachusetts, oucasional Papers 

of the Bost. Soc. Nat. Hist., 1880, iil. 280 pp., with map. 


Cunningham, Walter. 

Report of Walter Cunningham, late Mineral Agent on Lake Superior. Jan. 

8, 1845. Senate Docs., 23Lh Coug. 2d Sess., 1844-45, vii., No. 98, 
5 pp. 

Dana, James D. 

System of Mineralogy. 1st cd., New Haven, 1837, 671 pp. ; 2d ed., New 
York, 1844, 633 pp.; 3d ed.. New York, 1850, 711 pp.; 4th cd.. New 
York, 1854, 853 pp. ; 5th cd., New York, 1868, 827 pp. 

Manual of Mineralogy. New Haven, 1857, 456 pp. 

lleview of Marcou's " Geology of North America." Am. Jour. Sci., (2,) 
1858, xxvi. 323-333. 




Ecply to Prof. Agassiz on Marcou's " Geology of North America." Am. 
Jour. Sci., 1859, xxvii. 137 - 14-0. 

Mamiid of Geology. New York, 1st ed., 18C2, 800 pp. ; 2d ed., 1874. 

828 pp.; 3ded.', 1880, 911 pp. 
Manual of Mineralogy and Lithology. New York, 1878, 471 pp. 

Davies, D. C. 

Mctallil'crous Minerals and Mining, Loiidon, 1880, 432 pp. ; Copper Eocks, 
pp. 149 - 1G4 ; Iron Ores, pp. 274, 275. 

Dawson, John W, 

On the Gcologieal Structure and Mineral Deposits of the Promontory of 
Maiinaiisc, L. Sup. Canadian Nat. and Gcoh, 1857, ii. 1-12. 
Dawson, S. J. 

Keporton the Exploration of the Country between Lake Superior and the lied 
River Settlement, ete. S. J. Dawson and H. Y. Hind. Toronto, 1858. 
424 pp., with maps. 
Heport on the Exploration of the Country between Jjake Superior and the 

Red River Settlement. Toronto, 1859. 45 pp., with maps. 
Papers relative to tlie Exploration of the Country between Lake Superior and 
the Red River Settlement. S. J. Dawson, Henry Y. Hind, and others. 
Blue Book, 1859, SckSs. 2, xxii., 1G3 pp., with maps. 
D'Archiac, A. 

Progtes de la Geologic,- 1848, ii.. Terrain Quaternai-re, 3G9, 370; viii., For- 
jnation Tviassique, 635 - 644. 

Dearborn, H. A. S. 

On the Variations of Level in the Great North American Lakes, with Docu- 
ments. Am. Jour. Sci., 1829, (1,) xvi. 78 - 94. 
Delafield, Joseph, 

Notice of new Localities of Simple Minerals along the North Coast of Lake 
Superior, etc. Ann. Lye. of Nat. Hist., 1824. i. 79 - 81 
Delesse, A, 

Mines do Per des litats-Unis. Annales des Mines, 1857, (5,) xii. 805-841. 
Deroux, H. 

Die Kupfergruben des Oberen Scc's (Lake Superior). * Journal des Mines, 
18G0, vii.; Bci-g. u. lliitten. Zeit., 18G1, pp. 305-307, 329-331. 
Desor, Edward. 

Rain-Drop and Air-Bubble Impressions. Edward Dosor and J. D. Whitney. 
Proc. Bost. Soc. Nat. Hist., 1819, iii. 200, 201; 1851, iv. 131-133; 
Proc. Am. Assoc. Adv. Sci., 1851, v. 74. 

Sand Dunes and Rip])lc Marks on Lake Superior. Proc. "R'--^ Soc. Nat. 
Hist., "1849, iii. 207, 208 ; 1851, iv. 41, 42. 

Des Alluvions Marines ct Laeustrcs, et du Terrain erratlque de I'Amerique du 
Nord. Bull. Soc. Geol France, 1849-50, (2,) vii. 623-630. Sur Ics 
Drifts de rAuu'riqnc du Nord, 1851-52, ix. 94- 9G. Sur la Carte geo- 
logique du Lae Superieur, ix. 280, 281. Note sur le Terrain quaternaire 

■^ I 





de FAmerique clu Nord, 1851 - 52, ix. 2S1 - 285. Sur Ic Terrell dc Transi- 
tion ct qnaiernaire dcs fitats Unis, ix. 312-323. Ann. Sci. Diycov., 

1853, 2G9-272. 
Clay and Drift Deposits on Lake Superior. Proc. Bost. Soc. Nat. Hist., 

'l850, iii. 235, 236; Am. Jour. Sei., 1852 (2,) xiii. 93-109; Zeit. Deut. 

Gcol. Gesell., 1852, iv. 6G9-G79. 
Drift Stria; on Lakes Superior and Michigan, rroc. Bost. Soc. Nat. Hist., 

1850, iii. 242. 
" Cross Eormaiion " of Sandstone on Lake Superior. Proc. Bost. Soc. Nat. 

Hist., 1850, iii. 341. 
Parallelism of Mountain Chains in America. Proc. Bost. Soc. Nat. Hist., 

1850, iii. 380 - 382 ; Am. Jour. Sci., 1851, (2,) xii. 118 - 120. 
Origin of the Drift of Lake Superior. Proc. Bost. Soc. Nat. Hist., 1851, iv. 

Dunes on the Upper American Lakes. Proc. Bost. Soc. Nat. Hist., 1851, 

iv. 41, 42. 
Lake Superior. On the Silurian Hocks of the Lake Superior Land District. 

Proc. Am. Assoc. Adv. Sci., 1851, v. 04, G5. 
Post-Pliocene of the Southern States and its Belation to the Laurentian 
of the North and the Deposits of the Valley of the Mississippi. Am. Jour. 

Sci., 1852, (2,) xiv. 49-59. 
See Foetcr and Whitney. 

Dieffenbach, Otto. 

Bemerkungcn iiber den Kupfcrbergbau in den Yerclnigtcn Staatcn von Nord- 

Amcrika. Berg. u. Hiitten. Zeit., 1858, pp. 47, 48, 06- 08, 75, 70. 
Disturnell, John. 

The Great Lakes or Inland Seas of America. New York, 1803, 192 pp. 
and map. 

Douglas, James. 

The Native Copper Mines of Lake Superior. Quart. Jour. Sci., 1874, xi. 

162 - 180 ; Canadian Nat. and Gcol., 1874, (2,) vii. 318-336. 

Dupee, J. A. 

Ash-bed of the Phccnix Mine. Proc. Bost. Soc. Nat. Hist., 1855, v. 279, 


Dutton, T. R. 

Observation on the Basaltic Pormation on the Northern Shore of Lake Supe- 
rior. Am. Jour. Sei., (2,) 1847, iv. 118, 110. 

Eames, Henry H. 

^ Geological lleconnolssance of the Northern, Middle, and other Counties ot 

Minnesota. St. Paul, 1806. 58 pp. 
Eeport of the State Geologist, Henry H. Eamcs, on the Metalliferous Begion 

bordering on Lake Superior. St. Paul, 1866, 23 pp. 

Egleston, Thomas. 

Boracic Acid in Lake Superior Iron Ores. Trans. Am. Inst. Min. Eng., 1870, 
V. 131, 132. 



Copper Milling on Luke Superior. Trans. Am. Inst. Mia. Eng., 1877, vi. 

The Conglomcrak's of Lake Superior, and tlic Meikods of Dressing Copper. 
Trans. Am. Inst. Min. Eng., 1877, v. 000 ~ GIL 

Emmons, Ebenezer. 

Copper Mines of Lake Superior. American Geology, Albany, 1855, pp. 171 

Foster, J. W. 

On Certain Phenomena connected with the llise and Fall of the Waters of 

the Northern Lakes. Proc. Am. Acad., 1819, ii. 131-130; Ann. Sei. 

Biseov., 1850, pp. 245, 21.0 ; Edinburgh New Phil. Jour., 1850, xlix. 172. 
Catalogue of Eocks, Minerals, etc., collected by J. W. Poster. Smithsonian 

lleport, 1851, 381.-387. 
On the Antiquity of Man in North America. Trans. Chicago Acad. Sci., 

1807-09, pp. 927-257. 
Ancient Mining by the Mound-builders, in the " Pre-historic llaees of the 
United States.'' Chicago, 1873, pp. 301-374. 

Foster, J. W., and J, P. Kimball. 

Geology and Metallurgy of the Iron Ores of Lake Superior. New York, 1805, 
97 pp., with maj)s. 

Foster, J. W., and J. D. Whitney. 

Synopsis of the Explorations of the Geological Corps in the Lake Superior 
Laud District in the Northern Peninsula of Michigan. Senate Docs 
1849-50, iii., No. 5, 005-020. 
Ileport on the Geology and Topography of the Lake Superior Land District. 
Part L, Copper Lands. Executive Docs., 1st Sess. 31st Cong., 1849 - 50, 
ix., No. 09, 244 pp. with map; Am. Jour. Sci., 1851, (2,) xii. 222-239' 
Part II., The Iron Region, together with the General Geology, contains 
additional Ileports by James Hall, Edward Desor, Charles Whittlesey, 
and W. D. VVhiinoy. Senate Does., Special Sess. 32d Coug., 1851, iii.,' 
No. 4, 400 pp. with maps; Am. Jour. Sci., 1853, (2,) xv. 295, 29G ; 1854 
(2,) xvii. 11-38, 181-194. 

Ileport on the Iron District of Lake Superior. Senate Docs., 2d Sess. 31st 
Cong., 1850-51, ii.. No. 2. 147-152. 

Aperyu de rensembie des Terrains Siluriens du Lac Superieur. Bull. Soc. 
Geol. Prance, 1850, (2,) viii. 89-100. 

On the Azoic System, as developed in the Lake Superior Land District. Proc. 
Am. Assoc. Adv. Sci., 1851, v. 4 ~ 7. 

On the Age of the Sandstone of Lake Superior, with a Dcscrii)tiou of the Phe- 
nomena of the Association of Igneous Iloeks. Proc. Am. Assoc. Adv 
Sei., ]851, V. 22-38. 

On the Dilfcrcnt Systems of Elevation which have given Configuration to 
North America, with an attempt to Identify them with those of Europe. 
Proc. Am. Assoc. Adv. Sei., 1851, v. 130-151. 



On the Origin and Stratlgrnpklcal Kelations of the Trappcan Eocks of Lake 
Superior. Ann. Sci. Diycov., 1801, 285. 

Frazer, Persifor, Jr. . . 

The Lake Superior Copper Rocks in Pennsylvania, Trans. Am. Inst. Miu. 

Eng., 1870, vii. 336-339. 

FuUerton, T. M. 

St. Louis Hiver. Minn. Hist. Coll., 1850 - 56, i. 139 - 14-3. 

Geinitz, H. B. 

Alexander Winehell : iibcr geologischc Verhaltnisse in Michigan. Leonhard's 

Jahrbuch, 1876, pp. 438 - 440. 

Genth, Frederick A. 

Contributions to Mineralogy. Am. Jour. Sci., 1859, (2,) xxvii. 400; xxvni. 

24G-255; 1862, xxxiii. 190-206. 

Gray, A. B. . 

Keport of A. B. Gray on Mineral Lands of Lake Superior. Executive Docs., 

1st Sess. 29th Cong., 1845-46, vii., No. 211, 23 pp., with map. 
See John Stockton. 

Greeley, Horace, 

Process of Working a Lake Superior Copper Mine. Hunt's Merch. Mag., 

1848, xix. 559, 560. 

Hager, A. D. 

Ancient Mining on the Shores of Lake Superior. Atlantic Monthly, 1865, 

XV. 308-315. 

Hall, C. W. 

See S. F. Peekham and N. H. Winehell. 

Hall, Jannes. .... * t c • iok^ 

On the Silurian System of the Lake Superior Tiegion. Am. Jour, bci., 1854, 

(2,) xvii. 181-194. 
On the Potsdam Sandstone. Sixteenth Ann. Hep. of the Kcgcnts of the 

Univ. of New York. Appendix D. Albany, 1863, pp. 210 - 220. 
Bee Poster arid Whitney. 

Hanchett, Augustus H. 

* lleport on the Geology of Minnesota. 1864, 82 pp. 

Datolite' from Lake Superior. Proc. Post. Soe. Nat Hist., 1859, vii. 348, 
349,354; 1862, viii. 62 -64. 

Hector, James. ^ i .i t> -p rv 

On the Geology of the Country between Lake Superior and the Pacihc Ocean, 

etc. Quart. Jour. Geol. Soc, 1861, xvii. 388-445. 

See John Palliser. 

Henwood, William J. t^ -i j 

On the Native Copper of Lake Superior. On Metalhfcrous Deposits and 

Subterranean Temperature. Part. I, pp. 385-489; Trans. Geol. Soc. of 
Cornwall, vol. viii., Part I.; 1871, pp. 385 - 489. 




Hill, S. W. 

Copper Falls Mine. Mining Mag., 1854., ii. 068 - G72. 

Hind, Henry Y. 

licport on tlie Exploration of tlio Country between Lake Superior and tlie 

lied River Settlement. 1858, 425 pp., with maps. 
Ileport on the Assiniboine and Saskatchewan Exploring Expedition. 1859, 

201 pp., witli maps. 
Narrative of tiie Canadian Exploring Expeditions. London, 18G0, i. 494 pp., 

ii. 472 pp. 
See S. J. Dawson. 

Hitchcock, Edward. 

Outline of the Geology of tlie Globe. Boston, 1853, 1G2 pp., with maps. 

Hodge, James T. 

On the Mineral llegion of Lake Superior. Proc. Am. Assoc. Adv. Sci., 1849, 
ii. 301 - 303 ; Ann. Sci. DIscov., 1850, 2G0, 2G1. 

Houghton, Douglass. 

Ileport of Doctor Houghton on tlic Copper of Lake Superior. Nov. 14, 1831. 

lu the Discovery of the Source of the Mississippi, by II. R. Schoolcraft, 

pp. 287 - 292, New York, 1834. 
Pirst Annual Ileport on the Geology of Michigan, 1838. Lanman's History 

of Michigan, 1839, 347- 3GG; Am. Jour. Sci., 1838, (1,) xxxiv.190 -193. 
Second Annual Report of the State Geologist. Senate Docs., Michigan, 1839, 

2G4-294; Am. Jour. Sci., 1841, (1,) xl. 13G. 
Third Annual Ileport of tlic State Geologist, 1840. Senate Docs., Michigan, 

1840, GG-157. 

Pourth Annual Report of tlie State Geologist. Joint Does., Michigan, 1841, 

Pifih Annual Report of the State Geologist. Joint Docs., Michigan, 1842, 

Metalliferous Veins of the Northern Peninsula of Michigan. Am. Jour. 
Sci., 1841, (1,) xli. 183-180; Trans, of the Assoc. Am. Geol. and Nat., 
1840-42, pp. 35-38; Edinburgh New Phil. Jour., 1842, xxxiii. 201, 202. 

Copper on Lake Superior. Am. Jour. Sci,, 1844, (1,) xlvii. 107, 133. 


See T. B. Erooks, J. Honghton, Jr., J. H. llelfc, and H. R. Schoolcraft. 

Houghton, Jacob, Jr. 

The Ancient Copper Miners of Lake Superior. Iron, 1870, (N. S.,) viii. 108, 
1G9, 199; Swineford's Copper, Iron, and other Material Interests of Lake 
Superior. Marquette, 187G, pp. 78-89. 

Houghton, Jacob, Jr., and T. W. Bristol. 

Mineral Region of Lake Superior. Detroit, 184G, 109 pp. and map. Con- 
tains Re[>oris by Messrs. Burt, Ilubburd, D. Houghton, and Stannard. 

Hubbard, Bela. 

See Wilham A. Burt, J. Houghton, Jr., mid C7 T. Jackson. 




■ r 3 



_ -^ ■: _■^_ r-- 



Hughes, G. W. 

The Working of Copper Ore. Senate Docs., 1st Scss. 28tli Cong., 1843 ~ 44, 

v., No. 291, 58 pp. 

Hunt, T. Sterry. 

Oil some Ores of Nickel from Lake Superior. Am. Jour. Sci., 1855, (2,) xix. 

417, 418. 
Ou some Points iti American Geology. Am. Jour. Sci., 1861, xxxi. 392- 

414; Canadian Nat and GeoL, 18G1, vi. 81-105. 
Contributions to Lithology. Am. Jour. Sci., 1SG4, (2,) xxxvii. 248--20G; 

xxxviii. 91-104, 174-185. 
The Origin of Metalliferous Deposits. Trans. Am. Inst. MIn. Eng., 1872, 

i. 413-426. 
The Gcognostlcal History of tlie Metals. Trans. Am. Inst. Min. Eng., 1873, 

i. 331-336. 

Geognosy of tlie Appalachians and the Origin of Crystalline llocks. Proc. 

Am. Assoc. Adv. Sci., 1871, xx. 1-59. 
The Geology of the North Sliore of Lake Superior. (Supplementary Note.) 

Trans. Am. Inst. Min. Eng., 1873, ii. 58, 59. 
Chemical and Geological Essays. r>oston, 1874, 489 pp. Hevised Edition, 

Salem, 1878. 
The Development of Our Mineral Hesourccs. Harper's Magazine, 1875, li. 

Azoic Uocks, Part I., 1878. Second Geological Survey of Pennsylvania. E. 

253 pp. 
The Lake Superior Copper Hocks in Pennsylvania. Trans. Am. Inst. Min. 

Eng., lS79,vii. 333-336, 339. 
The History of some Pre-Cambrian llocks in America and Europe. Am. Jour. 

Sci., 1880, (3,) xix. 268-283. 

See T. C. Chamberlain and W. E. Logan. 

Irving, Roland D. 

On some Points in the Geology of Northern Wisconsin. Trans. Wise. Acad. 

Sci., 1873-74, ii. 107-119. 
On the Age pi the Copper-bearing llocks of Ln.kc Superior; and on ilie 
Westward Continuation of the Lake Superior ■Synclinal. Am. Jour. Sci., 

1874, (3,) viii. 46-56. 
Nolo oa the Age of tlic CryslalUne Pocks of Wisconsin. Am. Jonr. Sci., 

1877, (3,) xiii. 307-309.' 

Note on tkc Stratigraphy of the Iluronian Scries of Northern Wisconsin; 
and on the Equivalency of the Iluronian of the M.arquette and Penokee Dis- 
tricts. Am. Jour. Sci., 1879, (3,) xvii. 393-393. 

See T. C. Chamberlain. 

Jackson, Charles T. 

Minerals from Lake Superior. Proc. Post. Soc. Nat. Hist., 1844, i. 203 ; 

1845, ii. 57, 58. 



•. - 1 

* * 



Nature of Minerals aceonipanyiiig Trap Dykes wLicli interrupt "various Rocks. 

Proe. of the Sixth Ann. Meet, of tbc Assoc, of Am. Geol. and Nat., New 

Haven, 1845,29-31. 
On the Copper and Silver of KcAvcnaw Point, Lake Superior. Am. Jour. 

Sei., 1845, (1,) xlix. 81 -98; Proc. of the Sixth Aun. Meet, of the Assoc. 

of Am. Gcol. and Nat., New Ilavcn, 1845, 53 -GO. 
Sur *e Gisement de Cuivre et d'Argent natifs dcs Bords du Lac Superieur. 

Comptes Rcndus,1845, xx. 593-595; Bull. Soc. Gcol. Prance, 1844-45, 

(2,) ii. 317-319; L'Institutc, 1845, xx. 593-595; Leonhard's Jahr- 

buch, 1845, pp. 479, 480. 
The Copper and Silver Mines of Lake Superior. Proc. Bost. Soc. Nat. Hist., 

1840, ii. 110-114; Am. Jour. Sei., 1840, (2,) ii. 118, 119. 
Ilc]>ort on the Mineral Lands of Lake Superior. Contains llcports by Messrs. 

Locke, Channiiig, McNair, and Whitney. Senate Does., 1st Sess. 30th 

Cong., 1847-48, ii., No. 2, 175-230. 
Ores and Minerals from Lake Superior. Proc. Bost. Soc. Nat. Hist., 1847, 

ii. 250, 259, 200. 
Mineral Lands of Lake Superior. Contains llcports of J. W. Poster and 

J. D. Whitney. Senate Docs., 1848-49, 2d Sess. 30th Cong., ii., No. 2, 

153 - 103 ; Executive Docs., 1848 - 49, 2d Sess. 30th Cong., iii., No. 12, 

Beport on tlie Progress of the Geological Survey of the Mineral Lands of the 

United States in Michigan. Senate Docs., 1848 - 49, 2d Sess. 30lh Cong,, 

ii., No. 2, 185-191; Executive Docs., 1848 - 49, 2d Sess. 30th Cong., 

iii.. No. 12, 185-191. 
Copper of the Lake Superior llegion. Am, Jour. Scl., 1849, (2,) vii. 280, 

Lake Superior. Observations on the Mirage seen on Lake Superior in July 

and August, 1847. Proc. Am. Assoc. Adv. Sei., 1849, ii. 143-140; 

Proc. Bost. Soc. Nat. Hist., 1849, iii. 109. 

Remarks on the Geology, Mineralogy, aiul Mines of Lake Superior. Proc. 

Am. Assoc. Adv. Sei., 1849, ii. 2S3 ~ 288. 
On the Geological Structure of Keweenaw Point. Proc. Am. Assoc. Adv. 

Sei., 1849, ii. 288-301. 

Rcmarques sur la Geologic du District Metallifcre du Lac Superieur. Bull. 
Soc. Geol. France, 1849-50, vii. 007-073. 

Report on the Geological and Mineralogieal Survey of the Mineral Lands of 
the United States in the State of Micliigan. Contains Reports by Messrs, 
Jackson, Foster, Wliitney, Locke, Barnes, Burt, Hubbard, and others. 
Senate Docs., 1st Sess. 31st Cong., 1849-50, No. 5, iii. 371-935 ; Am. 
Jour. Sei., 1851, (2,) xi. 147, 148. 

Rcmarques sur la Geologic du District Metallifcre du Lac Superieur, suivi 
d'une courte Description de quclques-unes dcs Mines de Cuivre et d'Ar- 
gent. Extrait par M. Delcsse. Auuales des Mines, 1850, (4,) xvii. 103 



VOL. VII. — NO. 1. 




Age of the Lake Superior Sandstone. Proc. Eost. Soc. Nat. Hist., 184:3, iii. 

70, 11', 1850, p. 228; 18G0, vii. 30G-398. 
On Jacksonite. Proc. Bost. Soc. Kat. Hist., 1850, iii. 21-7, 248. 
Tormer Level of Lake Superior. Proc. Bost. Soc. Nat. Hist., 1850, iii. 292. 
On the Age of the Sandstones of the United States. Proc. Bost. Soc. Nat. 

Hist., 1850, iii. 385-339. 
Analyses of Pitehstone Porphyry from Isle lloyalc, etc. Am. Joiir. Sci., 

1851, (2,) xi. 401, 402 ; Proc. Bost. Soe. Nat. Hist., 1851, iv. 39, 40. 
Rain-Drop and Air-Bubble Impressions. Proc. Bost. Soc. Nat. Hist., 1851, 

iv. 131, 132. 
Geology, Mineralogy, and Topography of the Lands around Lake Superior. 

Senate Docs., 18*^51-52, 1st Sess. 32d Cong., xi. 232-244. In Andrews's 

Igneous Origin of Calcite Ycins. Proc. Bost. Soc. Nat. Hist., 1853, Pcb. 17^ 

iv. 308, 309. 
Ueber den Metallfiihrendcn Distrikt am Obern See im Staatc Michigan. 

Karsten's Archiv., 1853, xxv. G56-6G7. 
Catalogue of lloeks. Minerals, and Ores collected during the years 1847 and 
1848, on the Geological Survey of the United States Mineral Lands in 
Michigan. Collected by Charles T. Jackson. Smithsonian Report, 1854, 

pp. 338-3C7. 
Observations sur quelqucs Mines des l^tats-Unis et sur le Ores llougc du 

Lac Supericur. Comptcs Kendus, 1854, xxxix. 803-807. 
Trap Dikes. Proc. Bost. Soc. Nat. Hist., 185G, vi. 23, 24. 
On the Ash-bed and the Origin of the Copper. Proc. Bost. Soc. Nat. Hist., 

1855, V. 280, 281; 1859, vii. 31. 
Thermal Waters. Proe. Bost. Soe. Nat. Hist., 1859, vii. 45-47. 
Domcjkite from Lake Superior. Proc. Bost. Soc. Nat. Hist., 1801, viii. 258. 
Sur les Mines de Cuivrc du Lac Supercur ct sur un Nouvcau Gisement 

d'Ltain dans I'Etat du Maine. Compos llendus, 1809, Ixix. 1082, 1083. 
Bee James H. Kelfe. 

Bost. Soc. Nat. Hist., 1870, xiv. 

Jackson, Charles T., and J. B. Perry. 

Glacial Origin of Lake Superior. Proc. 


Jenney, F. B. 

iiee T. B. Brooks. 

Julien, Alexis A. 

See T. B. Brooks and T. C. Chamberlain. 

Keating, William H. 

Narrative of an Expedition to the Source of St. Peter's River, etc., performed 
in the Year 1823. 2 vols. i. 458 ; ii. 248, and app. 150. liondon, 1825. 

Kimball, J. P. 

On the Iron Ores of Marquette, Mieh. Am. Jour. Sci., 18G5, (2,) xxix. 

^^^ J. W. Poster. 



- 1 




Kneeland, Samuel. 

Coppci: ol" Lake Superior. Proc. Bost. Soc. Nat. Hist., 1857, vi. 283, 284. 

Koch, F. C. L. 

Kupfer- uud Eiseucrxc am Lake Superior. Zeit. Deut. Geol Gesells., 1851, 

Die MiucraLUegloncii der obcrcn TIalbinsel Micliigau's (N. A.) am Lake 
Superior uiid die Isle Koyal. Studieu des GoUiiigischeii Vereins berg- 
niiiiuuM'Uer Ereunde, von J. T. L. liausmann. 1854, vi. 1-248; The 
Miuiug Magazine, New York, 1353, i. 201~2GS. 

Lachlan, R. 

Ou the Periodical Rise and Fall of the Lakes.. Am. Jour. Sci., 1855, (2,) xix. 

00-71, 164-176; XX. 45-53. 

Lapham, Increase A. 

The Peuoklc Iron llange. Wise. State Agr. Soc. Trans., 1858 - 59, v. 391 - 

400, with map. 
See T. C. Chamberlain. 


LeConte, John L. 

On Coraeite, a new Ore of Uranium. Am. Jour. Sci., 1S74, (2,) iii. 173 - 

Lesley, J. P. 

Iron Manufacturer's Guide. New York, 1859, 772 pp., with maps. 

Locke, John. 

Geology of Porter's Ishmd and Copper Harbour. Trans. Am. Phlh Soc, 1844, 

ix. 311, 312, (pp. 305-315,) with maps. 
Geology and Magnetism. Smithsonian Contribuiious, 1851, iii., Art. L, pp. 

17''- 29. 
Catalogue of lloeks, Minerals, Ores, and Possils collected by John Locke. 

Smithsonian Report, pp. 1854, 367-383. 

See Charles T. Jackson. 

Logan, William E. 

North Shore of Lake Superior. Geol. Surv. of Canada, Rep. of Prog., 1846 

-47, pp. 5-46. 
Remarks on the Mining Region of Lake Superior, and a Report on Mming 
Locations claimed on the Canadian Shores of the Lake. Montreal, 1847, 

31 pp., with maps. 

Report on the North Shore of Lake Huron. Geol. Surv. of Canada, Mon- 
treal, 1849, 51 pp. 

On the Age of the Coppcr-bcariftg Rocks of Lakes Superior and Huron. Re- 
port of the Brit. Assoc. Adv. Sci., 1851, xxi., Trans. Sections, 59-02; 
Am. Jour. Sci., 1852, (2,) xiv. 224-229. 

Remarks on the Fauna of the Quebec Group of Rocks and the Primordial 
Zone of Canada. Am. Jour. Sci., 1801, (2,) xxxi. 210-220. 

Considerations rclathig to the Quebec Group and the Upper Copper-bearing 
Rocks of Lake Superior. Canadian Nat. and Geol., 1861, vi. 199-207; ■ 
Am. Jour. Sci., 1802, (2,) xxxiii. 320 - 327. 



Gcologj of Canada. Montreal, 1863, 98:3 pp., witli atlas. 

Kupferorze fiihrcndc Gcstcine am Obcrcn See. LeoiiLard's JaLrbucli 18G4 
p. 741. 

Geology of Canada. Ottawa, 18GG, 321 pp. Contains a Report on Lake 

Superior by Thomas Macfarlanc. 
Notes on the Report of Mr. Robert Eell on the Nipigon Region. Gcol. Surv. 

of Canada, Rep. of Prog., 1866-09, pp. 471-475. 

Logan, William E., and T. Sterry Hunt. 

A Sketeh of the Geology of Canada, in Canada at the Paris Exhibition, 1855, 
pp. 411-454. 

Lyell, Charles. 

New York Industrial Exhibition. Sir Charles Lyell's Special Report on the 
Geological, To[)ographicaI, and Ilydrographieal Departments. Blue Book, 
1854, xxxvi., 50 pp. Annalcs des Mines, 1854, (5,) vi. 1 - 83. 
Macfarlane, James. 

Geologist's Travelling Hand-Book. New York, 1878, 361 pp. 
Macfarlane, Thomas. 

On the Primitive Formations in Norway and in Canada. Canadian Nat. and 
Geol, 1802, vii. 1 - 20, 113 - 128, IGl - 171. 

Report on the Geology of Lake Superior. Geol. of Canada, 18GG, pp. 115 - 

On the Rocks and Cupriferous Beds of Portage Lake, Michigan. Canadian 

Nat. and Gcol, 1866-08, (2,) iii. 1-18; Geol. of Canada, 186G, pp. 
149 - 164. 

On the Geological Formations of Lake Superior. Canadian Nat. and Geol., 

1800 -08, (2,) iii. 177-202, 341-257. 
Dn the Geology and Silver Ore of Wood's Location, Thunder Cape, Lake 

Superior. Canadian Nat. and Geol., 1809, (3,) iv. 37-47, 459-463. 
Remarks on Canadian Stratigraphy. Canadian Nat. and Gcol., 1879, (2,) 

ix. 91-102. 

Marcou, Jules. 

lleponsu a la Lcttre dc MM. Foster et Whitney sur le Lac Supericur. Bull. 

Soc. Gcol, Franco, 1850, (3,) vilL 101-105. 
A Geological Map of the United States and the British Provnices of North 

America, with an Explanatory Text, Geological Sections, etc. Boston, 

June, 1853. 92 pp. . 

Esqnisse d'une Classification des Chaiues dc Montagues d'une Partie de 
FAmerique du Nord. Comptes Rendiis, 1854, xxxix. 1192-1197; An- 
nalcs des Mines, 1855, (5,) vii. 330-350; Mining Mag., 1856, vii. 321- 

Resume cxplicatif d'une Carte Gcologique des I^ltats-Unis ct des Provinces 
Anglaises de I'Amerique du Nord, avee un Profit Gcologique allant dc la 
Vallee du Mississipi aux Cotes du Pacifique, et tine Planchc dc Fossilcs. 
Bull. Soc. Gcol. France, 1854-55, (2,) xii. 813-936. 


I ! 



Die Geologic dcr Vcrcinlgteii Staaten und der Englisclien Provinzen von 

Nord-Amcrika von Jules Marcou. Petermann*s Gcographisclic Mittbei- 

lungeu, 1855, pp. 119-159. 
Geology of North America, with Three Geological Maps and Scvcu Plates of 

Possils. Zurich, 1858, UA pp. 
Reply to the Criticisms of James D. Dana. Zurich, 1859, 40 pp. 
Dyas et Trias ou le Nonveau Grcs Rouge en Europe dans rAmerique da 

Nord et dans I'lnde. Zurich, 1859, G3 pp. 
On the Primordial Pauna and the Taconic System. Proc. Bost. Soc. Nat. 

Hist., 18G0, vii. 309-382. 
Marteaux en picrre dcs ancicns Americalns, ponr I'Exploitation dcs Mines de 
Guivre ct d'Argcnt Natifs da Lac Snpericur, Comptcs Ilcndus, 1866, 

Ixli. 470, 471. 

Marvine, A. R. 

Geology of Michigan, Part II., 1873. 
See T. P. Prooks. 

Mather, W. W. 

Notes and Remarks connected with Meteorology on Lake Superior, etc. Am. 
Jour. Sci., 1848, (2,) vi. 1-20. 

McCracken, S. B. 

The State of Michigan, embracing Sketches of its 
sources, and Industries. Lansing,' 1870, pp. 48 ~ 


Position, Re- 

M'Kellar, Peter. 

* Mining on the North Shore of Lake Saperior. Toronto, 1874, 26 pp. 

McKenney, Thomas L. 

Sketches of a Tour to the Lakes. Baltimore, 1827, 493 pp. 
can Review, 1827, xxv. 334-352. 

McNair, D. K. 

See Charles T, Jackson. 

North Amcri- 

Mitchell, Samuel L. 

Native Copper of North America, 

Medical Repository, 1818, (2,) Iv. 101, 

Berg. Hi'itt 


Mosler, Chr. 

Der Kupfcrbergbau am Ohcrn See in Nordamerika. Zoitschr. 
Salin., 1877, Abhaudlungen, xxv. 203-221; 1879,.xxvli. 77 

Miillcr, Alb. 

Ueber die Kupferminen am Obern See im Staate Michigan, Nordamerika, 
Verhandhuigen der Naturforscheiulon Geselischaft in Basel. 1857, pp, 
411-438 ; Leouliard's Jahrbuch, 1857, pp. 79-82, 589, 590, 

Murchison, Roderick I. 

Slhiria. London, 1854, 523 pp. 

Murray, Alexander, 

North Shore of Lake Superior. 

Gcol. Surv. of Canada, 1840 - 47, pp. 





J I 

I ■ 




* Geology of Western Canada. Canadian Jour., 1854-55, (1,) iii 27-29 
48-52, 73-70. 

Murrish, John. 

Eeport: on tlie Geological Surrey of the Mineral Regions. Trans. Wise A^v 
Soc, 1872-73, pp. 4G9- 494. 

Newberry, J. S. 

Notes on tUe Surface Geology of the Basin of the Great Lakes. Troc. Bost. 

Soc. Nat. Hist., 1862, ix. 42-46. 
On the Surface Geology of the Basin of the Great Lakes and the Valley of the 

Mississippi. Ann. of the Lye. of Nat. Hist., 1870, ix. 213 - 234. * 
The Iron Resources of the United States. International Review, 1874 ii 


Nicholson, H. Alleyne. 

On the Geology of the Thunder Bay and Shabcndowan Mining Districts on 
the North Shore of Lake Superior. Quart. Jour. Geol. Soc., 1873, xxix. 


On the Mining District on the North Shore of Lake Superior. Trans, of 
North of England Inst, of Min. and Mccli. Eng. Neweastle-on-Tyne, 
1874-75, xxiv. 237-249, with maps. 

Noggerath, Johann Jacob, 

Von dem Gcdiegcn-Kupfer mit Gediegen-SIlber am den Gruben von Ketoena 

Point. Leonliard's Jahrbuch, 1848, p. 555. 
Owen, David D. 

Preliminary Report on the Geological Survey of Wisconsin and Iowa. Senate 
Docs., IstScss. 30th Cong., 1847-48, ii., No. 2,* pp. 100-174. 

Lake Superior. Report of a Geological Reconnoissance of the Chippewa Land 
District of Wisconsin, etc. Senate Docs., Ist Sess. 30th Cong., 1847-48, 
vii., No. 57, 134 pp. Am. Jour. Sci., 1850, (2,) x. 1 - 12. 

Abstract of an Introduction to the Final Report of the Geological Surveys 
made in Wisconsin, Iowa, and Minnesota in the Years 1847, '48, '49, and 
'50, containing a Synopsis of the Geological Features of the Country. 
Proc. Am. Assoc. Adv. Sei., 1851, v. 119-132. 

Report of a Geological Survey of Wisconsin, Iowa, and Minnesota. Am. 
Jour. Sci.; (2,) 1853, xv. 290-209; Philadelphia, 1852, 038 pp., with 
maps. Am. Jour. Sci., 1853, xv. 290 - 299. 

Catalogue of Geological Specimens collected by David D. Owen. Smithsonian 
Report, 1854, pp. 393-396. 

Description of two new Minerals and a new Earth. Jour. Acad. Nat. Sci. 

Phil, 1852, (2,) ii. 179-183; Am. Jour. Sei., 1852, (2J xiii. 420-423 ; 

Ann. Sci. Discov., 1853, pp. 290, 291. 
PaUiser, John, and James Hector. 

Papers relative to the Exploration of British North America. Blue Book, 

1859, Sess. 2, xxii., 64 ])p., with maps. 

Peckham, S. F., and C. W. Hall. 

Lintonite and other Forms of Thomsonite. Am. Jour, Sei., 1880, (3,) xix. 

— r^T".^'^'^-HJ ■^^'■"k^ -L- T- ".^-^->^.^■-. k— ^..-e^. — jn 

"HK^^I- Z^T*-W.-H I L-n-b — ^n-Mr^^ i vi --x 

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^—jj-j-^-^ — 






Miuing Mag., New York, 

perry, John B. 

See Chades T. Jackyon. 

Phillips, J. V. 

The Geology of ilic Upper Mississippi Lead Region. 
1854, ii. 129-138. 

Piggot, A. Snowden. 

Oil Copper and Copper Mining. Philadelphia, 1858, 388 pp.; Mining Mag., 
1858, X. 121-142, entitled History of the Co^jpcr Region of Lake Supe- 

Porter, George F. , 

Report on tlie Copper Rock. George P. Porter in Thomas L. McKenney's 
Tour to the Lakes, Baltimore, 1827, pp. 477, 478. 


Posselt, C. 

Die Kupfer-Disfcrikte des Obersee's, Lake Superior. Lconhard's Jahrbucli, 
185G, pp. 1-10. 

Preston, Samuel. 

Copper Ore on Lake Superior. Niles's Weekly Register, 183D, (3,) xii. 203, 

Pumpelly, Raphael. 

The Paragenesis and Derivation of Copper and its Associates on Lake Supe- 
rior. Am. Jour. Sei., 1872, (3,) iii. 188 - 198, 243-258, 347-353 ; Leon- 
liard's Jahrbueh, 1872, pp. 538-540; Geol. of Michigan, Part II., 1873. 
On Pscudomor])hs of Chlorite after Garnet at Spurr Mountain Iron Mine. 

. Am. Jour. Sci., 1875, (3,) x. 17-21. 
Metasomatie Development of tlie Copper-bearing Rocks of Lake Superior. 

Proe. Am. Acad., 1878, xiii. 253-309. 
See T. B. Brooks and T. C. Chamberlain. 

Rath, Gustav vom. 

Uebcr KalkspatU vom Oberen See. Pogg. Ann., 18G7, cxxxii. 387-404; 
Leonliard's Jahrbucli, 18G8, pp. 347, 348. 

Rawson, A. L,. 

Pictured Rocks of Lake Superior. Harper's New Monthly Mag., 1SG7, 
xxxiv. 681. 

Relfe, James H, 

Sale of Mineral Lands. Reports of Committees, 1845~4G, 1st Ses5. 29th 
Cong., iii.. No. 591, 51 pp. with map. Contains part of Douglass 
Houghton's Fourth Report, and some Analyses by Charlea T. Jack&ou.' 
Richardson, John. 

On some Points of the Physical Geography of North America in Conncctiou 
with its Geological Structure. Quart. Jour. Geol. Soc., 18131, vii. 212- 

Rivot, L. E. 

Mcmoirc sur Ic Giscment du Cuivre Natif au Lac Suporleur. Coraiptea- Ren- 

dus, 1855, xl. 1306-1309, 
Voyage au Lac Supericur. Annalcs dcs Mines, 1S55, (5,) vii. 173-^^8; 



J . 

■ r J 

I ■ J 

J ' 



Mining Mag., 1855, (1,) vi. 28-37, 99-lOG, 207-213, 4U-418; vii. 

2-19-355,359-307; 1857, ix. 00-05. 
Notice sur Ic Lac Supcricur. Annales dcs Mines, 1850, (5,) x. 305 -474. 
Ubcr die Kupt'crcrz-Lagcrsiatien am Obersce in den Nordamcrikanischen 

rreistaaten. Ecrg. u. Iliitten. Zeit., 1850, pp. 201 - 203, 209 - 271, 293 - 

295, 277-279, 314, 315, 317, 318, 325-328, 333, 334, 341-343,' 349- 

351, 357-359, 305-307, 381,382. 
Analysis of Lake Superior Iron Ore. Mining Mag., 1850, vii. 301. 
Rogers, H. D. 

Mineralogy and Geology of Lake Superior. Proc. Bost. Soc. Nat. Ilisi, 
1840, ii. 124, 125. 

Rogers, WilUam B. 

On tlie Origin of the Actual Outlines of Lake Superior. Proc. Am. Assoc. 

Adv. Sci., 1848, i. 79, 80. 
Age of the Sandstone. Proc. Bost. Soc. Nat. Hist., ISOO, vii. 394, 39o. 

Rolker, Charles M, 

The Alloucz Mine and Ore Dressing, as practised in the Lake Superior Cop- 
per District. Trans. Am. Inst. Min. Eug.,1877, v. 584-600. 

Rotninger, Charles. 

Observations on the Ontonagon Silver Mining District and tlic Slate Quarries 

of Huron Bay. Geol. Surv, of Michigan, 1876, iii. 153 - 100. 
See T. B. Brooks, Geol. Siii'v. of Michigan, 1873, i., Part III. 

Rottermund, Count de. 

lleport on the Exploration of Lakes Superior and Huron. Canada Legisla- 
tive Assembly, 1856, 24 pp. ; Canadian Jour., 1856, (2,) i. 440 -452. 

Ruggles, D. 

Tides in the North American Lakes. Am. Jour. Sci., 1843, (1,) xlv. 

Considerations respecting the Copper Mines of Lake Superior. Am. Jour. 

Sci., 1845, (1,) xlix. 04-72. 

Russell, John L. 

Wood from the Terraces of Lake Superior. Proc. Bost. Soc. Nat. Hist., 

1850, iii. 273. 

Sanders, George N, 

Mineral Lands of Lake Superior. Senate Docs., 2d Sess. 28tli Cong,, 1844- 

45, vii., No. 117, pp. 3 - 9 ; xi.. No. 175, pp. 8 - 14. 
See John Stockton. 

Sauvage, E. 

Notice sur les Minerais de Per du Lac Supcricur. Annales dcs Mines, 1875, 
(7,) viii. 1-35. 

Schoolcraft, Henry R, 

Narrative Journal of Travels throus^h the Northwestern Bej^ions of the United 

Slates, extending from Detroit through the Great Chain of American 

Lakes to the Sources of the Mississippi River. Albany, 1821, 419 pp. 
with map. 



". -■- h . 



Account of tlic Native Copper on tlic Southcni Sliorc of Lake Superior, witk 
Historical Citations and Miscellaneous Kemarks, in a Report to the De- 
partment of War. 1821. xVm. Jour. ScL, 1S21, (IJ iii. 201 - 21G ; 
Quart. Jour. Sei., 1822, xii. 422 - 423. 

On the Number, Value, and Position of the Co])per Mines on the Southern 
Shore of Lake Superior. Senate Papers, 2d Sess. 17th Cong., 1822, 

Doc. 5, 33 pp. 

Notice of a llcccntly Discovered Copper Mine on Lake Superior, "witli several 
other Localities of Minerals. Am. Jour. Sci., 1824, (1,) vii. 43-49. 

Narrative of an Expedition througli the Upper Mississippi to Itasca Lake, the 
Actual Source of this llivcr. New York, 1834, 307 pp. with map.. Con- 
tains a Report by Dougkiss Houghton. 

Localities of Minerals observed in the Northwest in 1831 and 1832. Dis- 
covery of the Source of the Mississippi, pp. 157 - 159. New York, 1834. 

On the Product ion of Sand Storms and Lacustrine Beds by Causes associated 
with the North American Lakes. Proc. Brit. Assoc. Adv. Sci., 1842, xii. 
Trans. Sections, 42-44; Am. Jour. Sci., 1843, (1,) xliv. 3GS - 370. 

A Memoir on the History and Physical Geography of Minnesota. Mimi. Hist. 
Coll., 1850-50, i. 108-133. 

Summary Narrative of an Exploratory Expedition to the Sources of the 
Mississippi lliver in 1820, resumed and completed by the Discovery of 
its Origin in Itasca Lake in 1832. Philadelphia, 1854. Purports to con- 
tain many of the original Reports to the War Department, and other 

Selwyn, Alfred R. C. 

Notes of a Geological Reconnoissancc from Lake Superior to Port Garry. 

Gcol. Surv. of Canada, Rep. of Prog., Montreal, 1872-73, pp. 8-18. 
The Stratigraphy of the Quebec Group and the Older Crystalline Rocks of 

Canada. Canadian Nat. and Geol., 1879, (2,) ix. 17 - 32 ; Geol. Surv. of 

Canada, Rep. of Prog., 1877-78, A. 15 pp. 

Shepard, Charles U. 

On the Copper and Silver of Kcwenaw Point, Lake Superior. Proc. of the 

Sixth Ann. Meet, of the Assoc, of Am. Gcol. and Nat., New Haven, 1S45, 
CO, 01. 

Tautolite on the North Shore of Lake Superior. Am. Jour. Sci., 1847, (2,) 
iv. 278. 

Shepherd, Forrest. 

Remarks on a Boulder Mass of Native Copper from the Southern Shore of 
• Lake Superior. Am. Jour. Sci., 1817, (2,) iv. 115, 110. 
Observations on the Drift, Furrows, Grooves, Scratches, and Polished Surfaces 
of the Rocks of Lake Superior. Am. Jour. Sci., 1847, (2,) iv. 282, 283. 

Spencer, Joseph William, 

Lake Superior. — On ttie Niplgon or Copper-bearing Rocks of Lake Superior, 
wiih Notes on Copper Mining in that Region. Canadian Nat. and Geol., 

1878, (2J viii. 55-81. 

,. 1 



Stanard, B. A. . „ , t tt i 

Stanard's Hock. In tlie " Mineral Regions of Lake Saperior, by J. liougli- 

ton, Jr., and T. W. Bristol, page 81. 

Stevens, William H. 

The Prospects of the Lake Superior Mining licgion. Mining Mag., 1854, u. 


Stockton, John. 

Report ou the Mineral Lands of Lake Sapcrior. Senate Docs., 18M-4o, 
2d Scss. 28tli Cong., xi., No. 175, 22 pp. with map. Contains reports by 
Messrs. J. B. Campbell, George N. Sanders, and A. B. Gray. 

Strong, Moses. 

See T. C. Chamberlain. 

Sweet, E. T. 

Notes on the Geology of Northern Wisconsin. Trans. Wise. Acad., 1875 - 76, 

iii. 40-55. 
See T. C. Chamberlain. 

3wineford, A. P. 

History and llcvlcw of the Copper, Iron, Silver, Slate, and other Material 

Interests of the South Shore of Lake Superior, Marquette, Mich., 1876. 

Contains Ancient Copper Miners, J. Houghton, 78-89; C. E. Wright, 

Geology of tlic Lake Superior Iron District, 132 - 145. 

Tamnau, F. . -r» r* i 

Minerals from the Copper District of Lake Superior. Zcit. Deut. Geol. 

Gesells., 1852, vi. 3 - 0, 9, 10 ; 1854, vi. 11 ; Leonhard's Jahrbuch, 1854,, 
442, 443 ; 1855, 349.,^ 

Teschemacher, J. E. 

Harmotomc and Volborthite from Lake Superior. Proc. Bost. Soc. Nat. 
Hist., 1849, iii. 105, 106. 

Tod, David. 

See William Bartllt. 

Tuttle, H. B. 

See T. B. Brooks. 

Verneuil, Edouard P. de. 

Lettrc sur la Geologic des ]5tats-Unis. 

(2,) iv. 12, 13. 

Whiting, Henry. 

Remarks on tlie Supposed Tides and Periodical Rise and Pall of the Noi^th 

American Lakes. Am. Jour. Sci., 1831, (1,) xx. 205-219. 

Whitney, J. D. . -n t 

Description and Analysis of Three Minerals from Lake Superior. Bost. Jour\ 
Nat. Hist., 1847, 'v. 486-489; Am. Jour. Sci., 1848, (2,) vi. 269, 270. 

Jacksonitc, a New Mineral from the Lake Superior Region. Proc. Bost. Soc. 
Nat. Hist., 1848, iii. 5, G. 

Bull Soc. Geol. Prance, 1846 - M, 

1 I 

I : 

■ !| 

; F 




Cklorastrolite, from Tsle Royale, Lake Superior. Proc. Bost Soc Nat 
Hist, 1848, iii. 13, 

Cliemical Examination of some American Minerals, Bost. Jour. Nat. Hist., 

1850-57, vi. 30-42; Proc. Bost. Soc. Nat. Hist, 1848, iii. 78, 79 j 

Am. Jour. Sci, 1849, (2,) vii. 434, 435. 
Black Oxide of Copper at Copper Harbor, Lake Supenor. Proc. Bost. Soc. 

Nat. Hist., 1849, iii. 102, 103 ; Ann. Sci. Discov., 1850, pp. 201 2G2 ■ 

Am. Jour. Sci., 1849, (2,) viii. 273, 274. 

The Lake Superior Copper and Iron District. Proc. Bost. Soc Nat Hist 
1849, iii. 210-212. 

Practurc of Slate at tlie Jackson Porge. Proc. Bost. Soc. Nat. Hist 1850, 
iii. 220. 

Catalogue of the Rocks, Minerals, etc., collected on the District bet\yccn 

Portage and Montreal River, during the Years 1847 and 1848, by J. D. 

Whitney. Smithsonian Report, 1854, pp. 387-392. 
Tlie Metallic Wealth of the United States. Philadelphia, 1854, 510 pp. 
Review of Murchison's Siluria. Am. Jour. Sci., 1855, (2,) xix.' 371-385. 
Remarks on some Points connected with the Geology of the North Sliore' of 

Lake Siiperlor. Proc. Am. Assoc. Adv. Sci., 1855, ix. 204- 209. 
On the Occurrence of the Ores of Iron in the Azoic System. Proc. Am 

Assoc. Adv. Sci., 1855, ix. 209-210 ; Mining Mag., 1856, vii. 07-73| 

Am. Jour. Sci., (3,) 1850, xxii. 38 - 44. 
Notice of New Localities, and Lzteresting Varieties of Minerals, in the Lake 

Superior Region, sn])plemcntary to the Chapter on this subject- in Part 

IL of the Report of Poster and Whitney. Am. Jour. Sci.," 1859, (2,) 

xxviii. 8-20; Mining Mag., 1800, (2,) i. 32 -47. 
Note on the Geological Position of the Lake Superior Sandstone. Minin 

Mag., 1800, (2,) i. 435-440. 

On the Chemical Composition of Pectolite. Am. Jour. Sci.. 1800, (2 1 xxix 
205-208. ^\ ^J —• 

See Edward Desor, Poster and Whitney, and Charles T. Jackson. 
Whitney, William D. 
See Poster and Whitney. 

Whittlesey, Charles. 

On the " Superlleial Deposits " of the Northwestern Part of the United States 
Proc. Am, Assoc. Adv. Sci., 1851, v. 54-59. 

On the Ancient Mining Operations on Lake Superior. Proc. Am. Assoc 
Adv. Sci., 1857, xi. 42-44. 

Pluctuations of Level in t1ie North American Lakes. Proc Am Assoc Adv 
Sci., 1857, xi. 154-100. 

On the Origin of the A..oic Rocks of Michigan and Wisconsin. Proc. Am 
Assoc. Adv. Sci., 1859, xiii. 301-308. 

On Plueiuations of Level in the North American Lakes. Smithsonian Con- 



I >l 


tributions to Knowledge, 1859, xii.. No. % 25 pp. 



The Penokic Mineral Eange, Wisconsin. Proc. Post. Soc. l^at. Hist., 18G3, 

ix. 235-244. 
On the Movements of tlic Glacial Era in tlie Yallcy of the St. Lawrence. 

Proc. Am. Assoc. Adv. Sci., 1866, xv. 43-54. 
On the Prcsh- Water Glacial Drift of the Northwestern States. Smithsonian 
Contributions to Knowledge, 1806, xv. 1-32; Smithsonian Report, 1860, 

Abstract of Eeraarks npon the Occurrence of Iron in Masses. Proc. Am. 

Assoc. Adv. Sci., 1867, xvi. 97-107. 
On the Cause of the Transient Fluctuations of Level in Lake Superior. Proc. 

Am. Assoc. Adv. Sci., 1873, xxii., Part IL, 42-46. 
Sudden Eluctuations of Level in Quiet Waters. Ilccords of Observations. 

Proc. Am. Assoc. Adv. Sci., 1874, xxiii. 139-143. 
Physical Geology of Lake Superior. Proc. Am. Assoc, Adv. Sci., 1875, 

xxiv. 60 -72. 
On tlie Origin of Mineral Veins. Proc. Am. Assoc. Adv. Sci., 1876, xsv, 

See T. C. Chamberlain, and Poster and Whitney. 

Iluronian Clay Slates. Quart. Jour. Gcol. 

Wichmann, Arthur. 

A Microscopical Study of some 
Soc, 1870, XXXV. 156-104. 
See T. C. Chamberlain. 

Wight, O. W. 

See T. C. Chamberlain. 

Williams, C. P., and J. F. Blandy. 

Some Coutributious to a Knowledge of the Constitution of the Copper 
of Lake Superior. Am. Jour. Sci., 1862, (3,) xxxiv. 112-120. 

P an gc 

Wilson, Daniel. 

The Ancient Miners of Lake Superior. 

The Southern Shores of Lake Superior. 


Canadian Journal, 1856, (2,) i. 225 
Canadian Journal, 1856, (2,) i. 344- 

Winchell, Alexander. 

Pirst Biennial Keport of the Progress of the Geological Survey of Michigan. 

Lansing, 1861, 339 pp. 
■ Notice of a small Collection of Possils from the Potsdam Sandstone of Wiscon- 
sin and the Lake Superior Sandstone of Michigan. Am. Jour. Sci., 1804, 

(2,) xxKvii. 226-232. 
-^^ Geological Map of Michigan. Philadelphia, 1866. Leonhard's Jahrbuch, 

1808, pp. 99-101. 
The Isothermals of the Lake Ecgion. Proc. Am. Assoc. Adv. Sci., 1870, 

xix. 106-117. 
The Diagonal System in the Physical Eeatures of Michigan. Am. Jour. Sci., 

1873, (30 vi. 36-40. 





Winchell, N. H. 

Tlic Gkciul features of Grocn Bay of Lake Micliigan, with some Observa- 
tions on a Poriuer Outlet of Lake Superior. Am. Jour Sci 1871 CS ) 
ii. 15-20. " '^ '^ 

The Geological and Natural History Survey of Minnesota. 1873-1878. 
7 volumes. Geology of Lake Superior, 1st, 2d, and 7th vols. The last 
contains a Report by C. W. llall. 
Wright, Charles E. 

Pirsfc Annual Report of the Commissioner of Mineral Statistics of the State of 

Michigan for 1877-78. Marquette, 1870, 239 pp. 
See T. B. 13rooks, T. C. Chamberlain, aud A. P. Swincford. 

■ si 




Figure 1 (pnge 30) represents the contact of tlio jasper and ore on the left hand 
with the schist on the right. This section shows the relations of the banding of the 
jasper to the line of junction. Lake Superior Mine, Islipcming. 

Figure 2 (page 30) represents in plan tlie projection of the handed jasper on the 
left into the schist on the rigl:^ the banding running parallel to the walls. Lake 
Superior Mine, Ishpeming. 

Figure 3 (page 30) represents in section a dike of very fair hematite ore, extend- 
ing across the lamination of the schist. Lake Superior Mine, Ishpeming. 

Figure 4 (page 31) is a section showing the relations of the branching dikes of 
hematite to the schist. Cleveland Mine, Ishi)eming. 

Figure 5 (page 31J shows in section the relation of the jasper and ore to the un- 
derlying schist. Jackson Mine, Negaunee. 

Figure 6 (page 31) shows in section the relations of the hematite to the schist. 
The hematite projects in a large knob dike mass up into tlie schist, and is connected 
with the main body of ore below. Jackson Mine, I^Tcgaunee. 

.BiilJ. Mii:^.eirm Conip 


Y ^ 





Figure 7 (pago 31) rcprosciits n, section of a dike of iron ore extending across tlic 
lamination of the schist. Jackson Mine, Negannee. 

FiauuE 8 (pages 81, 32) represents in section the relationn of a dccontposed hema- 
tite (" soft hematite") to tlie schist. In tliis case the curvature and dislocation of 
the schist by the npthrust of the ore is well shown, as represented along the curve 
h, c. Of our own knowledge we cannot state that the part a belongs to the hematite 
on the riglitj as i-cprosented. Jackson Mine, Negaunee. 

Ei(;i;uE 9 (page 32) showy a section of jasper and ore intniding in a wedge- 
shaped mass obli^ptely through the scliist. Jackson Mine, Negaunee. 

Figure 11 {page 32) represents in section the intrusion of ore m a dike of varying 
dimensions between an<l across the laminae of the schist, bending them In different 
directions, as shown to a certain extent in the figure. Jackson Mine, Negannee. 




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FiaiTKE 10 (page 32) represents in section the ore passing around and cutting olT 
a portion of the schist, some six feet in length, from the main body. The ore at the 
lower portion of the figure was then being mined, the schist forming a horse iu 
it. Jackson Mine, Negaunee. 

FiouKE 12 (page 32) shows the relations of ore, wliich was then being mined, to 
its overlying schist. This represents a section some twenty feet in length. Jackson 
Mine, Negf,unoe. 

FiGriiE 13 (page 32) represents a section of a jasper dike in a sandstone. The dike 
is of irregular width, and approximately follows the stratification of the sandstone in 

its main course. It sends projections in places out across the lamlnai, breaking, con- 
torting, and indurating them. The dike is some fifteen feet in length, and in the 
figure its width has bocu greatly exaggerated compared with its lengtli. Home Mine, 

Cascade Range. 

eiiiD, to nip. 








Figure 14 (page 30) represents in plan a "ilioiite" dike witli a tongue extended 
into tlie schist. Ligiit-house Point, ilarquotte. 

Fir.UKE 15 (page 36) shows in plan the line of juiietion ol" a " diorite " with the 
seliist. Quarry near Light-house, Marquette. 

FiouRi-: 16 (pages 36, 38) shows in plan tlie relations of a felsite, represented on 
tlie right of the figure hy angular marks, to a later "diorite" dike and to the schist. 
The '* diorite" cuts and faults the felsito, hut as the portion to the left of the "dio- 
rite" is under the waters of the lake, the writer is not sure of the accuracy of tliat 
portion of tlie figure. 

FluuuFi 18 (pEige 41) shows in plan tlie lino of junction hctweeu the "diorite" and 
schist. East of Ishpenang. 

FiGUJ^K 19 (page 41) shows in plan the lijie of contact between the " diorite " and 
schist, witii an enclosed fragment of schist in the "diorite." Northeast of the 
Clevcliuid Mine, Ishpeming. 

FiauuE 20 (page 41) is a section, chiefly ideal, showing the supposed relations of 
the " diorite " dike to the adjacent schist, at the same locality as Fig. 19. 

Fjoure 21 (page 41) represents in plan the line of junction hetween the " diorite" 
and schist. Northeast of tlie Cleveland Mine, Ishpeming. 


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FiGiTUE 17 (page 39) shows in plan tlic relations of tlic granite denoted by the 
crossed (+) space to the "diorite." The *'diorite" shows in mass on the left, and 
in rounded fragments in the granite. Picnic Point, north of Marfjuette. 

Figure 22 (page 41) represents the line of junction between the ''diorito" on the 
right with the schist on the left. Kortheast of the Cleveland Mine, Ishpeming. 

Figure 23 (pages 49, 50) represents a plan, partly ideal, of a narrow diabase dike 
cuttinc^ a broad "diorite" dike and the schists at Ishpeming. The lettering is ex- 

plained in the text. Salisbury Mine, Ishpeming. 

Figure 24 (pages 49, 50) is an ideal section showing the supposed relation of the 
above "diorite" to the schists. Salisbury Mine, Islipeming. 




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FirxiTRE 25 (page 51) sliows in section tlie relation of the *'soft hematite," repre- 
sented by ova] marks, to the jasper and ore above and on both sides of it ; also to fis- 
sures which allow tlie percolation of water, the upper portion of the figure being 
adjacent to the surface of the ground. McConiber Mine, Kegaunee. 

FiGL'Rio 26 (page 55) shows in section reddish eruptive granite cutting gray gneiss. 
The granite at the left and bottom of the figure is connected with the main body of 
the granite. South of Isbpeming. 

Figure 27 (page 113) represents in section a tongue of trap extending down into 
the ash-bod, and holding a rounded fragment of the latter. End of drift, Sept. 12, 
1879, 5th level. Copper Falls Mine, Keweenaw Point. 

FiGURTi 28 (page 113) shows the denuded and irregular surface of the undeilyiiig 
sandstone, covered by the overlying lava flow. Emerson Adit, Copper Falls Mine, 
Keweenaw Point. 

All the figures, except when otherwise stated, are from freediand sketcdics made in 
the held from actual observed occurrences. No attempt has been made to draw to 
scale, or to show anything except the actual relations of the rocks to one another. 
The sketches were redrawn by the writer, engraved on stone by I\Ir, L, Ttouvelot, 
and printed by A. Meisel. 


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No. 2. — The Felsites and their Associated Eochs North of Boston. 

By J, S. DiLLEK. 

The extremely interesting and complicated petrology of Eastern 
Masyacliusetts has been the subject of a great deal of discussion, and 
at no time in the past have opinions concerning the origin and relations 
of the rocks been more at variance than at present. It is important, 
therefore, that the facts to be found in nature be carefully observed and 
described in order that the various differences of opinion may, as far as 
possible, be removed and the truth demonstrated. There are, however, 
certain localities whose facts appear, under the eyes of some observers 
to be very different from those seen by other observers in the same place ; 
and it seems necessary in such cases, where the facts are questioned, to 
describe them with more than usual detail. 

The field we have explored includes Melrose, Maiden, and the southern 
portions of Medford, Stoneham,* Wakefield, Saugus, and Lynn. Within 
this area felsite is the chief rock, and with it are associated, besides a 
complex group of tufaceous rocks, commonly called breccias, a group 
of stratified rocks, granites, dioritos, slates, and diabases. The recent 
"Contributions to the Geology of Eastern Massachusetts," by W. 0. 
Crosby, contains a map upon which the general distribution of the 
rocks, so far as we know, is quite correctly given; but, as Mr. Crosby 
is doubtless well aware, there are many places, and some of them im- 
portant, too, where the map is in error. We cannot expect to have for 
many years to come a very accm-ately detailed geological map of this 
neighborhood, for even if we had, what we have not, a correct topo- 
graphical map to use as a basis of geological work, the extreme com- 
plexity of the rocks, together with their highly altered condition and 
the existence of quite extensive covered areas must necessarily require 
a longtime for correct delineation. In determining the relative age of 
eruptive rocks we have been guided by the generally accepted criterion, 
viz. that of two rocks, the one which penetrates the other in dike-like 
masses or contains fragments of the other is the younger. In consider- 
ing the rocks associated with the felsites, we shall notice them in the 
order of their ages, beginning with the oldest, and endeavor to describe 
the facts apart from theoretical considerations. 

VOL. VIL — NO. 2. 11 



Stratified Group. 

The name stratified group is applied to certain rocks whose only 
common character is that of stratification; and although tho rocks of 
the Boston basin, and also some of the so-called breccias, arc distinctly 
stratified, there is no difiSculty in separating the first group, at least 
geographically, from the others, for its distribution is widely different. 
The stratified group, consisting chiefly of quartzito and argillaceous 
rocks, forms an important area, extending from Medford northeast across 
Spot Pond and Melrose into Saugus. It is a long, narrow band, and 
fortunately it adjoins the granite, felsite and dioritc, so that we have 
upon the borders of this area the means of determining the relations 
of all of the rocks mentioned. The petrological relations of this group 
and its probable much wider distribution upon tho surface in former 
times will be considered later. 


The granite occuxjies a large area in Medford southwest of Spot Pond, 
and also in the eastern part of Melrose, cxtendiug into central and 
northern Saugus. In Maiden there are four small areas of granite, one 
near Pleasant Street between Maiden and Medford, another northeast of 
Prospect Hill, a third along the Newburyport turnpike north of Broad- 
way station, and a fourth near Franklin Park. 

The relation of the granite to the stratified group is shown by many 
facts so evident, that, as far as the phenomena themselves are concerned, 
there is no difference of opinion among observers. 

North of Howard Street, along the Melrose-Saugus line, and at otlier 
places, the granite occurs in oblong or irregular patches, apparently as 
an eruptive in the stratified group. The facts in these cases are, how- 
ever, not as convincing as others so abundant throughout the regions in 
which the granites predominate. It has been frequently observed that 
upon Marblehead Neck the coarsely crystalline granite coutains frag- 
ments of distinctly stratified rocks. In the granite of Medford stratified 
fragments arc abundant, and sometimes at a considerable distance from 
the nearest large outcrops of their parent rock. This is especially the 
case with those found near the western base of Pine Hill. The granite 
in a beautifully glaciated exposure near the west end of Long Pond, 
Melrose, envelops several angular pieces of rock in which the stratifi- 
cation can be readily traced. ' Similar phenomena may be observed upon 




the western shore of Trankcr's Pond, Saugus, and Wenunchus Lake, 
Lynn. A very fine example of sti;aii(ied inclusions within the granite 
has been pointed out by Mr. Crosby * at Break-heart Hill, Saugus. The 
best exposures at this locality are not far from forest Street, on the west 
side of a private road loading from Mr. Artemus Edmond's northward 
towards Pleasant Lake. The coarse-grained granite makes very clearly 
defined contacts with the stratified rocks which it envelops, and the 
fragments in which the stratification is prominent are large and lunner- 
ous, and the facts so evident that they cannot bo questioned. It is 
interesting to notice that tJie strike and dip of the planes of stratifica- 
tion are about the same in all of the enveloped fragments (strike N. 5 
10° E. Dip 90°). This phenomenon is developed in a very remarkable 
degree about half-way between Oakland Vale and Long Pond, where the 
granite is full of elongated fragments whose stratification is nearly verti- 
cal, and whose strike is approximately N. 40" E. This direction corre- 
sponds very nearly to a sort of gneissaid arrangement of the minerals in 
the coarse granite of adjacent localities where the fragments do not occur. 
Almost all the varieties of rocks which occur in the stratified group are 
represented by fragments in the granite. The fragments vary in size 
from an inch to many feet in length, and are generally more highly 
metamorphosed than the large mass of the group from which they were 
derived. The (piartzite, although occurring in very wc. marked frag- 
ments, is not nearly so abundant as the less sihcious varieties. 

It is probable that the position of tlie fragments, in some cases at 
least, as well as the gneissoid structure found in the same region may 
indicate the direction of motion in the enveloping mass at the time of 
its extrusion. The general distribution of the fragments of the strat- 
ified group, throughout a greater portion of the granites we have exam- 
ined, forces us to admit, cither that the granites have moved quite a 
long distance from the present outcropping stratified group, or else 
that the latter group at the time of the eruption of the granites had a 
wider distribution. The large dike of diabase at the west base of Pine 
Hill, Medford, contains quite a number of fragments which closely 
resemble the quartzite of the stratified group. If thoy are fragments of 
quartzite from the stratified group, they must have been brought from 
beneath the. surrounding fclsite, either from the stratified group in place, 
or an included fragment in the granite. Such facts render it probable 
tliat before the granites and felsites reached the surface, the stratified 
group had a much wider distribution than it has at the present time. 

* Contributions to tko Geology of Eastern Jtassacluisetts, p. 39. 






The fclsitGS, extending from Medford through Maiden, Melrose, and 
Sangus to the eastern part of Lynn, and northward from Melrose into 
Wakefield, are the prevailing rocks of that region. Their petrological 
relations have been one of the chief enigmas in the geology of Eastern 
Massachusetts, and, judging from the present diverse opinions, much 
thorough work needs to be done before a final solution is reached. Most 
observers agree that the fclsites are of more recent age than the granites j 
nevertheless, there is a wide difference of opinion concerning the phe- 
nomena upon which this common conclusion is based. Some observers 
maintain that the felsite is younger than the granite, from the fact, as 
they say, that the felsite not only envelops detached fragments of the 
granite, but also penetrates it, in the form of distinct dikes. Other ob- 
servers reach the same conclusion, because, in their opinion, the granite 
envelops felsitic fragments, and in the form of irregular dikes pene- 
trates the felsite. 

it is evident that theoretical considerations are of little value unless 
supported by facts, and for this reason the latter should be clearly set 
forth and particularized, apart from theories, so that there may be some 
hope of securing, ultimately, a uniformity of opinion concerning at least 

what occurs in the field. 

As far as our observations have extended, we have never seen an exam- 
ple of the granite breaking through the felsite or enveloping its frag- 
ments. In every case in which we could determine the relations of the 
rocks the felsite occurred as an eruptive penetrating the granite. 

Before proceeding to point out the special localities in which the gran- 
ite is cut by the felsite, let us consider the evidence, apart from the dikes, 
which proves the truly igneous nature of the latter rock. 

Upon Break-heart Hill in Saugua and to the west towards Main Street 
there occurs an extremely heterogeneous mixture of banded felsite with 
grayish fragmental material, which in its external aspect resembles, to a 
considerable extent, ordinary ashes. The true nature of this grayish 
rock was not suspected until the microscope revealed the :ict that it 
contains many of the splinter-shaped or chip-like sharp-edged fragments 
whose peculiar forms belong to the volcanic glass of rhyolitic tufas. The 
forms are so characteristic, and in this case so well preserved among the 
other ashy material, that there can be no doubt of their identity. The 
fragments, as we would expect,* are no longer volcanic glass, hut quartz, 

* On the Classification of Kooks, by M. E. Wadswortli ; Lull. Mas. Coiiip. Zool. 
at Cambridge, Mass., Vol. V., No. 13. 



which is the product of alteration. The composition of this interesting 
rock, and its potrologic relations, wc believe, establish beyond question 
that it is a veritable ancient volcanic ash. There is considerable 
evidence, though not yet decisive, for want of further microscopical inves- 
tigations, that these ashes are distributed in patches througliout a con- 
siderable portion of the region occupied by the felsites. 

It seems to be certain, therefore, tliat there has been within this re- 


gion a true volcanic outburst by which the ashes were produced, and 
that anterior to the formation of the ashes, or perhaps about the same 
time, there was an eruption of felsitic hiva, with which the ashes became 
entangled in the complicated manner we find upon Break-heart Hill. 

The banding so well marked in the felsites upon the western shore of 
Marblehead Neck until (piite recently has been considered stratification, 
and therefore appeared to be a fatal argument against the theory of 
those who regard the felsites as exotic. Dr. Wadsworth was the first to 
consider the banding a fluidal structure, equivalent to that so prominent 
in the modern rhyolitcs, and consequently of igneous origin. It is of 
common occurrence, especially in the silicious felsites of Lynn, Saugus, 
and Melrose ; and from the fact that where it is found in felsite, forming 
distinct dikes or tongues in the granite, or enveloping fragments of other 
rocks, the banding is parallel to the line of contact, there seems to be no 
good reason for doubting that it was produced by the flowing of the fel- 
sitic matter in a state of fusion. The extreme complexity of the band- 
ing upon Break-licart Hill and at places in Marblehead Neck cannot be 
satisflictorily explained by any other supposition, and it is scarcely nec- 
essary to add that under the microscope the phenomena of the banding 
are wholly at variance with those found in sedimentary rocks and com- 
pletely in harmony with those of altered rhyolites. The banding, there- 
fore, instead of furnishing an argument in fivor of the sedimentary 
origin of the felsites, is proof of tlieir eruptive character. 

Since the relation of the felsite and granite has been the subject of 
such discrepant statements, we shall point out the localities in which, as 
it seems to us, the relation is clearly exposed. Within the granite 

southwest of Spot Pond a dike of somewhat piidcish felsite occurs near 
the top of a high hill west of the north end of Brooks's Lane, where it 
enters Forest Street. Further northward and nearer to Forest Street 
there are, at least half a dozen smaller dikes of a similar felsite in the 
granite. That these masses of felsite are true dikes and not included 
fragments witliin the granite is proved by the fact that they not only 
scud irregular tongues of felsite from tha main dike into the adjoining 



rock, but also that they hold within thcmsGlves detached fragments of 
the granite which they penetrate. The small patch of granite northeast 
of Prospect Hill, Maiden, is penetrated by one of the largest fclsitic 
dikes of this region. It may be seen in the clitf directly opposite Fanlk- 
ncr's station. . Along the Newburyport turnpike in Maiden there is a 
small area of granite to which we have elsewhere * alluded. Mr. Crosby f 
regards this rock as granitoid potrosilex. We placed it among the gran- 
ites not only on account of its granitic structure, but from the fact that 
it is clearly distinct from the adjoining feisite. In a gravel-pit upon the 
east side of the turnpike, a short distance north from Salem Street, sev- 
cral junctions of the granite and feisite may be scon. The feisite is in 
some places slightly banded along the contact, and the lino of junction 
between the two rocks can be readily traced from the south part of the 
gravel-pit for a considerable distance over the hills to the eastward. 
Passing a short distance northward along the turnpike several low clilfs 
appear upon the left. In the second of these, two well-marked dikes of 
reddish feisite occur. One of them is about five feet in width, tlie other 
about twelve feet, and they cut through an almost vertical cliff of the 
granite twenty-five feet in height. These dikes may be traced at intervals 
for nearly a quarter of a mile to the northeast. The granitic rock of this 
area, as well as that northeast of Prospect Hill, is quite different in its 
general aspect from the granite of the larger areas to the northward ; but, 
so far as the facts are known, there seems to be no good reason for sup- 
posing that it is not granite, or that its relation to the feisite is different 
from that of the other granites. 

The large granitic mass extending from eastern Melrose into central 
and northern Saugus is bounded upon the south and east and partly upon 
the west by feisite, so we would expect to find within this area numerous 
exposures of the two rocks in contact, and thereby determine their rela- 
tions. Near the eastern end of Long Pond in Saugus there are several 
distinct dikes of feisite in the same granite which at the west end of the 
pond, about one fourth of a mile distant, as already mentioned, contains 
well-marked inclusions of the stratified group. One of the most dis- 
tinctly marked dikes may be found upon the eastern end of the granite 
hill north of Essex Street, about a quarter of a mile northwest from the 
Newburyport turnpike. The strike of the dike is N. 20° E., and it 
varies, within a distance of sixty feet, from six to ten feet in width. 

The most interesting and instructive exposures of the stratified group, 

* Proo. Bost. vSoc. Is^at. TTIst., A'ol. XX., p. 357. 

'[■ ContributioTis to tlu; Geology of I''asteni Mas.sjiolinsetts, p. 78. 

* ft 



granite and felsite near together, are to be found upon Break-heart Hill in 
Saiigus. It in to this locality that Mr. Crosby refers when ho says : * 
" On the high hills to the west of the private road running from Forest 
Street and Central 13rook to Water Street we have, perhaps, the faiest 
example of the extravasation of the granite yet observed in this region. 
The exposures of the rock here are remarkably good ; and the granite 
is coarse and sharply defined where it penetrates the adjoining petrosilex 
and liorubleude slate in irregular dykes, or envelops isolated masses of 
these rocks that have been wrested from the parent beds." 

Concerning the fact that the granite envelops detached fragments of 
the stratified group there can bo no doubt • but when we come to exam- 
ine the relations of the felsite and the granite, the evidence is not so 
easily deciplicrcd. The top of the hill is composed of a mixture of 
felsite and volcanic ashes, which extends over the southeastern slope, 
meeting the rocks of the stratified group ; to the northward, a short 
distance, this mixed mass is liautcd by the coarsely crystalline granite 
containing the stratified fragments ; and to the westward it connects 
with a large area of similar rocks forming the high hills near by in that 
direction. Within the small area of this complex rock there are two 
patches of granite. One of these, with a diameter of about twenty-five 
feet, upon the western brow of the hill, has its side penetrated by a 
tongue, at least six feet in length, of very distinctly banded felsite. 
The banding is also very distinctly marked at several places along the 
periphery of the granite, and in every case it is parallel to the line of 
contact between the two rocks. Tlie smaller patch of granite upon the 
southern slope of the hill is completely enveloped by felsite. Although 
the felsite in this case is not banded, it apparently sends tongues into 
the granite, and, near the junction of the two rocks, it envelops small 
fragments of the larger mass which it surrounds. Although there are 
other exposed contacts of the felsite and granite in the neighborhood, 
none were observed to furnish important evidence bearing upon the 
relations of the two rocks. The banding of the felsite is undoubtedly 
of igneous origin, and its occurrence about the granite, together with 
the tongues of felsite penetrating the granite, and fragments of the 
latter rock enveloped by the former, are phenomena which, as it seems 
to us, can be explained only by supposing that the felsite flowed through 
and around the granite. 

The well-marked dikes of felsite cutting the granite between Fishing 
Point and Phillips Beach on the Swampscott coast, as first pointed out 

*' Contributions to the Geology of Eastern Massachusetts, p. 78. 



by Dr. Wadsworth, as well as the numerous examples found upon the 
coast of Marblehead Neck, conclude an array of facts which establish, 
beyond dispute, not only that the felsite is a truly eruptive rock, but 
also that in every case where we could deterniiue its relation it is 
younger than the granite which it penetrates. 

The relation of the felsite to the stratified group is the subject of very 
different opinions, and for this reason it seems proper to present in 
detail the evidence we have observed bearing upon this question. If 
the phenomena described sustain the conclusions already drawn, viz. 
that the stratified rocks of Medford, Stoneham, Melrose, and Saugus 
are older than the eruptive granites of that region, and that the felsite 
is a truly eruptive rock younger than the granites, it is evident that 
there can be no gradual passage from the felsite into the stratified 

Mr. Crosby,* who has done so much on the geology of Eastern Massa- 
chusetts, refers to the region west of the Boston and Maine liailroad in 
Melrose as the one which "places beyond question the fact that there 
is a gradual transition between the quartzite and petrosilex, and that 
portions of the latter rock are intercalated in the stratified group." 
This group is well exposed near the railroad, a short distance south of 
the Melrose station, and extends so.uthwestward, parallel with the 
general strike of the formation, across Spot Pond into Medford. Excel- 
lent outcrops, perhaps the best of the stratified group in this region, 
form a part of the northern shore of the pond. The felsites and strati- 
fied rocks are exposed within several hundred yards of each other upon 
opposite sides of Washington Street, Melrose, a short distance east of 
the Melrose-Stoneham line. The exposures in both cases are within 
the regions marked felsite by Mr. Crosby. Those upon the north side 
of Washington Street are distinctly sedimentary rocks, while the rocks 
in the cliOs to the southward arc well-marked felsite, slightly porphy- 
ritic, of the kind forming the mass of the Maiden Highlands. Although 
I have examined several times the region between Spot Pond and Long 
Pond, where the stratified group meets the felsite to the southward, I 
have not been able to find the two rocks in place exposed nearer to 
each other than at the locality described ; and although in the present 
state of our knowledge the existence of a *^ gradual transition " or inter- 
calated felsite in the stratified group cannot be denied, it may be stated 
that careful search has not revealed to us the slightest evidence in favor 
of Mr. Crosby's positive assertion. It is hoped that the exposures 


* Contiibutions to the Geology of Eastern Massachusetts, p. lOG. 

\ t . 

J ■- 




which place such an important fact beyond question will be described 
in detail, so that other observers may obtain the evidence. 

Fortunately we need not depctid for a knowledge of the relations of 
the rocks in question upon a region in which the absence of exposures 
along the line of contact renders it difficult to tell what may be true. 
Upon the northern boundary of the stratified group, from Break-heart 
Hill westward towards Main Street, the relations of the rocks are clearly 
exposed. Between Break-heart Hill and Main Street several distinct 
contacts of the felsite and quartzitc may be seen, and there are no indi- 
cations whatever of a transition between the two rocks. It will bo 
remembered that, in describing Break-heart Hill, it was mentioned that 
the complex mixture of felsite and ashes extends from the suuunit down 
the southeastern slope to t}ie rocks of the stratified group. Near the 
middle of the slope facing Mr, Edmond's house is a small ledge, furnish- 
ing an excellent exposure in which the felsite, with contorted banding, 
overlies unconformably at a large angle the upturned edges of the 
stratified group. The rocks beneath are in part quartzite interstratified 
with other rocks of the same group, and the lino of contact sloping down 
the hill is w^ell marked. A short distance to the eastward the banding 
in the felsite and the distribution of the ashy material has the samo 
general slope as the plane of contact. 

It seems to us that this very interesthig exposure phices beyond the 
possibility of a doubt the conclusion that the felsite is younger than the 
rocks upon which it i*eposes. A few rods to the southwest' of the ex- 
posure just noticed there is another, which shows apparently one side 
of a dike of felsite cutting through the stratified rocks. The lino of 
contact is very distinctly marked and irregular, like that of an eruptive 
rock, and is at right angles to the bedding of the adjoining rocks. 
Distinct fragments of quartzite belonging to the stratified group are 

enveloped by the felsite of this locality, and small ones have been found 
embedded in the ashes. 

The facts observed upon Break-heart Hill are in harmony with the 
relative positions of the two rocks as determined by the relations of both 
to the granite, and there appears to be no doubt that the stratified rocks 

of Melrose and the adjoining towns are older than either the granite or 

Having considered the relations of the older rocks to the felsitcs, let 
us turn our attention to the relations whioii the felsitcs hold to one 
another. Mr. Crosby has shown that the rocks of the group vary widely 
in chemical composition, and Dr. Wadsworth has called attention to 




the fact that upon Marblehcad Neck the fclsitcs arc not all of tho 

same age. 

The stratified group which we have already described separates the 
adjoining felsitcs into two distinct areas, each of which includes several 
felsites of different periods of eruption. The felsite which is so inti- 
mately associated with the ashes upon Breakdicart Hill occupies a con- 
siderable portion of the area east of Main Street, and between Break-heart 
and Little Castle Hills. A junction between the dark-colored felsite and 
a pale pink felsite may be traced across the northern part of Little 
Castle Hill, and southwest of this hill, about halfway to Main Street, 
another distinct junction occurs along which there is \cvy well marked 
banding in the light-colored felsite, showing that it is the younger. 
Neither of those felsites is very porphyritic. 

Within the southern area, a short distance southeast of Long Pond, 
Saugus, there is a small patch of a ree., chiefly non-porphyritic felsite. 
The region immediately south of the pond, and to tho southwest as far 
as the Boston and Maine Eailroad, is occupied by a felsite which is 
generally very porphyritic. The ground-mass of this felsite varies 
somewhat in color, but it is usually light pink or pale purple, and 
besides being the most completely and uniformly porphyritic felsite of 
this region, very frequently envelops fragments of older rocks. It might 
properly be designated the porphyritic, pebble-bearing felsite, for these 
two features are comparatively uniform throughout the wide area occu- 
pied by this beautiful rock. The red non-porphyritic felsite, to which 
we have already referred, forms a very clearly marked junction with the 
porphyritic felsite about one fourth of a mile southeast of the eastern 
end of Long Pond, and the porphyritic felsite, which is distinctly banded 
along the lino of contact, penetrates the adjoining red felsite, and en- 
velops many of its fragments. Among the enveloped fragments in the 
porphyritic felsite are found a few of granite, — a fact which accords witli 
those we have already discussed in showing that the gi\anitcs arc older 
than tho felsites. The pebbles of the old felsite are numerous and widely 
distributed in the porphyritic felsite, and the evidence is so complete 
and well marked, that, as it seems to us, there can be no doubt that 
the two felsites were extruded at different periods. 

About a third of a mile southeast of Swain's Pond in Melrose the 
porphyritic felsite is cut by a dike of what appears to bo a third felsite, 
which is non-porphyritic and of a gi'ay color. The dike has very irregular 
junctions, varies in width from a foot to eighteen inches, and can be 
traced across an exposiu'c for a distance of thirty feet. The youngest 

« « 



of the felsitcs does not appear to have a very extensive development 
in that region. 

Within the folsites many junctions of apparently different rocks 
may he seen ; but because, as it appears to us, it may be possible for dif- 
ferent parts of the same eruptive mass to form distinct junctions with 
each other, we were not inclined to accept junctions alone as evidence 
of difference in age unless supported by other facts. It appears to be 
evident, however, that not only at Murblchcad Neck, as shown by Dr. 
Wadsworth, but also in each of the two areas of felsite we have explored, 
there were at least two distinct eruptions of felsite. 

That some of the felsitcs arc distinct in age is clearly shown also by 
their relations to the fragmental rocks, the so-called breccias, with which 
they are associated ; but these relations can be considered to better ad- 
vantage after the latter rocks have been described. 

Fragmental Rocks, 

The complex group of rocks included mider the above name embraces 
tlioso commonly called breccias in this vicinity, and is composed of 
members wholly distinct in origin and composition. The coarse frag- 
mental rocks, whose fragments may be either angular or well rounded, 
are perhaps more abundant than the sandstone and finer-grained rocks, 
Most of these rocks arc composed of fragments of highly altered igneous 
rocks, the felsitcs and granites, and properly belong to the tufas, or, accord- 
ing to Dr. Wadsworth's classification,* the porodites. There are, however, 
a number of localities where the conglomerate is composed chiefly of 
pebbles of quartzite from the stratified group. 

The volcanic ashes to which we have already referred as occurring In 
the neighborhood of Breakdicart Hill are undoubtedly of igneous origin, 
but in other regions the material is distinctly stratified, and must have 
been produced by aqueous agencies. Although we have no evidence 
which proves certainly the relative age of the ashes, it seems probable, 
from the fact that they are so intimately mixed with the oldest felsite, 
that they were produced aboTit the same time with the felsite, and earlier 
tlian the stratified porodites (tufas) and conglomerates. It is sometimes 
extremely difficult to distinguish in the field between a recomposed rock 
and an eruptive one which has, at tlie time of its extrusion, picked up 
many fragments. t Only those exposures which arc quite certainly of 

■ * Bulletin of ilio Mus. Coiitp. Zool., Cambridge, Muss., Vol. V., No. 13, p. 280. 
^(U! paper l)y the writer. Troc. B. S. N". H., Vol. XX. 355. 



sedimentary origin will be noticed ; although they are quite numerous, 
they are comparatively amall. Mr. Crosby was the first to notice the 
stratification of these rocks, and pointed out the locality at Dungeon 
Rock, Lynn, where the material is fmc, and apparently all derived from 
the felsites. Another similar locality in which the stratific:ition is well 
marked occurs along the water-pipe between the reservoir and the water- 
works, Lynn. In these areas it is almost impossible to tell, upon a 
weathered surface, that the rock is fragmentaL 


exposures were 

accidentally brought to light by quite extensive excavations, and it is 
possible that some of what is now regarded as felsite may be a rccom- 
posed rock, so like felsite (from which it was made) in its external 
appearance as not to be distinguished from it by the unaided eye. The 
area of porodites and conglomerates of Vinegar Hill and Pirates' Glen 
is probably the largest area of these rocks in this region. In the same 
locality there are several small patches of granite mixed with the frag- 
mental rocks which are in places distinctly stratified. 

One of the most interesting exposures of the stratified porodites is 
upon a high hill, a short distance south from Saugus, and near the east 
side of the road leading to Sweetser's Corner. The greater portion of 
the hill is felsite, but upon its northern slope occurs the most beautiful 
coarse tufa of this region. It is tilted so as to be standing nearly or 
quite vertical, with a strike N. 70° E. At this place the thickness, 
measured directly across the strike, is about 150 feet, and may be greater, 
but for want of exposures the excess beyond 150 feet cannot be deter- 
mined. This is the only locality we have found to furnish an opportu- 
nity to determine the thickness of the fragmental rocks. 

An exceptional conglomerate occurs a short distance west of the 
Saugus station, near the railroad. Its peculiarity consists in its associa- 
tion with the granite, and that it is composed almost wholly of granitic 
dcbi'is. Some of the pebbles are large and well rounded, and the mass 


seems to lie directly upon the rocks from which it was derived. An 
unsuccessful attempt has been made to use this material for the bases 
of gravestones. 

Between Cliftondale station and the Newbury port turnpike there is 
quite a large area of conglomerate containing a considerable proportion 
of quarts^itc pebbles. A smaller area of finer material occurs near the 
end of Granite Street, by the spring, about a third of a mile north of 

A most interesting and varied locality in which the stratification is 
well marked may he found about a third of a mile southeast of Swain's 



Pood iu Melrose. Although tho locality is small, it embraces a variety 
of fiiie-grained, red, argillaceous rocks, sandstones, and a very coarse con- 
glomerate composed almost wholly of pebbles of quartzite from the 
stratified group. 

In the base of a small hill a short distance northeast of Oak Grove 
station, on the Boston and Maine Eailroad, the fragmental rocks of this 
group arc well exposed. They extend into the base of Prospect Hill, 
and on the opposite side of the valley are exposed near the bas6 of 
the Maiden Highlands. Within the Highlands there are two small 
areas of tufas, oue on each side of Highland Avenue along the Malden- 
Medford line. The conglomerate of West Mcdford, which is well de- 
veloped along Purchase and Mystic Streets, resembles to a considerable 
extent some parts of the Roxbury conglomerate ; but Mr. Crosby is most 
likely correct in connecting it with the fragmental rocks so intimately 
associated with the fclsite. 

Within the felsitcs north of the stratified group we have found only 
two small areas which, as it seems to us, are of sedimetitary origin. One 
of the patches lies upon the first hill north of Oak Street, a sliort dis- 
tance w^cst of Nahant Street (Main Street), Wakefield, and the other 
is upon Candle-wood Hill, northeast of the Stoneham station on the 

Boston and Maine B,ailroad. It is very probable that a number of areas 
of sedimentary rocks have escaped our notice, but we feel sure they do 
not occupy the large areas over which they have been represented to 
extend. The very porphjTitic fclsite occupying the region lying between 
Long Pond, Saugus, and the Maiden Highlands contains, as we have 
already stated, many pebbles of other felsites, and some of granite, but, 
like that at Eed liock, Lynn, it is by no means of sedimentary origin. 
We have elsewhere * shown that some of the felsites are younger than 


the fragmental rocks so intimately associated with them, and it remains ' 
in this connection to jjoiut out tho facts upon which this inference 
is based. 

In the conglomerate about a fourth of a mile north of Cliftondalc 
station there is a dike of pinkish fclsite which is clearly eruptive 
through the fragmental rocks of the same locality. A similar phenome- 
non may bo »cen north of Oak Street, Wakefield, where a distinct tongue 
from the black-edged dike penetrates the adjoining fragmental I'ocks. 
The best locality, however, for observing the relations of these rocks is 
southeast of Swain's Pond, where the porphyritic felsite not only pen- 
etrates in the form of small, irregular dikes the fragmental rocks, but. 



* Proc. Bo8t. Soc. Nat. Hist., Vol. XX., p. 364. 
NO. 2. 12 



also in one exposure distinctly overlies them. This relation enables 
us to understand how it happened that the coarse quartzose conglomerate 
is completely surrounded by fclsite which does not appear to have en- 
tered into its composition. The porphyritic fiilsite being younger than 
the fragmental rocks, it is not difficult to explain the fact that it contains 
so many pebbles. In Prospect Hill, Maiden, and the small hill near by, 
just northeast of the Oak Grove station, the porphyritic felsite appar- 
ently overlies the fragmental rocks of the same locality. The dark- 
colored, less porphyritic felsite of the Maiden Highlands is closely related 
to the porphyritic one to the eastward, and there is good reason to be- 
lieve that the former, hke the latter, is younger than the tufas of that 
region. The tufaccous rocks along the Malden-Medford line north of 
Highland Avenue are composed almost wholly of \orj silicious felsites, 
unlike those by which the small area is completely surrounded ; a fact 
which, as it seems to lis, can be explained most satisfactorily by sup- 
posing that the dark felsite of the Highlands had not been spread upon 
the surface in its present position at the time the fragmental rocks were 
formed. The evidence we have given seems to us sufficient to fully 
cstabhsh the conclusion that some of the felsites are younger than the 
fragmental rocks with which they are intimately associated ; and on 
the other hand, it cannot be doubted that these fragmental rocks are 
more recent than the felsites of whose debris they arc largely composed. 


The diorite adjoins the felsite for only a few miles along the north- 
western boundary of the latter, between Melrose Highlands and Smith's 
Pond (Crystal Lake), Wakefield. The line of contact is generally cov- 
ered, and the two rocks were not seen upon the same exposure north of 
West Hill, near the Stoneham station * on the Boston and Maine Hail- 
road. Upon this interesting hill we find a complex mixture of almost 
all the rocks of the region, and it appears to us that the diorite pene- 
trates and envelops not only the stratified group, but also the granite 


and felsite. Distinct fragments of the granite and felsite have been 
seen in the diorite at several places. Similar phenomena may be seen 
upon the hills in Stoneham, near the south side of Franklin Street, 
where the eruptive diorite penetrates the granite, and cuts directly 
across the bedding of the stratified quartzites and schists. In that region 
the granites, dioritcs, and rocks of the stratified group are intermingled 

* The name of the poat-otlice -at Stoncliain station is Melrose Highlands. 



in a very complicated manner, but we have not been able to find any 
evidence which would Jcad uy to suppose that there is a gradual transi- 
tion from any one of the rocks into another of the same locality. It 
seems evident to us that the dioritcs are truly eriiptive rocks, and that 
their extrusion has taken place since that of the granite and felsite 
which they penetrate. 

Diabase and molaphyr, so abundant in the neighborhood of Boston, 
are found in very distinct dikes, cutting all the other rocks, and close 
the series of eruptive rocks in which there seems to have been, in the 
order of extrusion, a general progress from silicious to basic rocks. 

The relative ages of the rocks in the region we have explored, as it 
seems to us, have been pretty clearly established, but the position of 
the whole series in the geological column is a matter concerning which 
we have seen very meagre and conflicting evidence. The slates, sup- 
posed hy some to be primordial, lying between the Charles River and 
the hills of Medford and Maiden, have not been found, so as we 
know, in contact with the eruptive rocks to the northward. On the 
north side of the Saugus branch of the Eastern Eailroad, between 
Faulkner's station and Maplewood, the slates arc exposed within about 
one hundred and fifty feet of the lulls of eruptive rocks upon the north 
side of Salem Street. The slates dip steeply {66") to the northward, as 
though they were plunging beneath the other rocks. It may have been 
this fact which led Prof John W. Webster, many years ago, to assert 
that the transition rocks (slates, etc.) were overlain hy the porphyries of 


In the rocks of the stratified group, so far as we know, fossils have 
never been found; and were it not for the fact that the Iloxbury con- 
glomerate contains numerous pebbles of quartzite, apparently derived, 
at least in part, from the rocks of tlie stratified grouj), I can sec no good 
reason for supposing the stratified group to be prc-pahcozf>ic. The same 
conglomerate contains pebbles of felsitc, but whether any of them are 
from the felsites now exposed along the northern margin of the Boston 
basin is a question which, for its satisfactory solution, will require much 
more thorough and careful work than has yet been done in this region. 





The facts we have observed in the region described in the foregoing 
paper appear to establish, for that region, the following conclusions : 
The stratified group contains the oldest rocks of which we have any 



knowledge in that region, and, before the extrnsion of the more recent 
eruptive rocks, they probably had a much wider distribution upon the 

surface than they now have. 

The granites are not derived by metamorphism from any part of the 
series of rocks (stratified group) which they envelop, but are truly 
eruptive rocks, whose extrusion has occurred since the formation of the 
stratified group. Tiierefore the granites, as we know them in their 
present position, are younger than the stratified group. 

The felsites are eruptive rocks, more recent than the granites. There 
were at least two eruptions of felsite in each ai'ea, and in the southern 
area there were probably three eruptions. 

The fragmcntal material associated with the felsite upon Break-heart 
Hill is a volcanic ash ; elsewhere the fragmental rocks have generally 
been formed of material eroded and deposited by water. 

The very porphyritic felsite between Long Pond and Prospect Hill, 
part of the felsite of Wakefield and at Cliftondale, and jjrobably the 
dark-colored felsite of the Maiden Highlands, are younger than the 
tufas and conglomerates with which they are associated. 

The diorites are eruptive, and younger than the felsites. 

The diabases and melaphyres are the youngest eruptive rocks of this 
region, and there has been, in the order of eruption beginning with the 
granites, a general progress from silicious to basic rocks. 



No. 3. 

On an Occitirence of Gold in Elaine, By M. E, 



The gold under consideration here is found on Seward's Island, a 
small island in the town of Sullivan, Hancock County. The gold is 
found in quartz veins cutting an eruptive mass of diabase. This diabase 
forms a dike of about 40 foot in thickness, lying approximately parallel 
to the bedding of an indiu'ated fine-grained argillaceous mica schist ; 
all dipping nearly S. 30^ W., 24° to 42^ The dip averages about 35^, 
and the strike is far from being uniform. Crossing the diabase at various 
angles, but generally from north to south, are segregated quartz veins. 
In some places the rock is a confused i-eticalated mass of these veins, with 
patches of diabase lying between them. The veins vary in width from 
a mere seam to even a foot in breadth. Stai^ting whore only one or a 
few of them are visible, they gradually increase in number until they 
become quite numerous, while they will doubtless be found to fade 
away as they began. The diabase and schists are cut by several dikes 
of diabase running approximately at right angles to the strike of the, 
schist, or parallel to the veins. The vein stone is quartz, together 
with some calcite, tremolite, and chlorite^ and carries tctradymite and 

So far as examination has been made, the veins in the diabase carry 
gold, and the decomposed diabase immediately adjacent to the quartz 
veins also contains that metal to a greater or less extent. The gold 
occurs principally in small grains in the vein in connection with the 
tetradymitc, bits of decomposed diabase, and in the cavernous portions, 
but not in the compact quartz of the vein itself. The tctradymite is 
in irregular grains and masses, showing a brilliant metallic lustre and a 
well-marked basal cleavage. The locality is worked for its gold, and 
was visited by the writer in December last. 

Cambridge, Mass., January, 1881. 



VOL. VTl. — NO. 3. 





No. 4:. ~~ A Microscojncal Sttuly of the Iron Ore, or Peridotite, of 
Iron Mine Hill, Giiviberland, Rhode Island. Bij M. E. Wads- 


The attention of the writer was first particularly called to tliis forma- 
tion by some specimens presented to him by Mr. H. 11 Metcalf in the 
spring of 1880. These did not appear to the writer to be any common 
ore of iron, but rather fragments of a basic eruptive rock containing 
much iron. Sections were accordingly made which revealed its true 

The formation was described by Dr. Charles T. Jackson in his repoi't on 
the Geological Survey of lUiode Island in 1810. lie states that Iron 
Mine Hill *' is a mountain mass of porphyritic niagnctic iron ore, 4G2 
feet iu length, 132 feet in width, and 104 feet in height above the 
adjoining meadow. From these measurements, which were made over 
only tlie visible portion of this enormous mass of iron ore, it will appear 
that there arc G,312,33G cubic feet of the ore above natural drainage. 
. . . Its specific gravity is from 3,82 to 3.88. . . . This ore is remark- 
able both on account of its geological situation and its miueralogical 
and chemical composition. It appears to have been protruded through 
the granite and gneiss at the same epoch with the elevation of numerous 
serpentine veins which occur in this vicinity. This will appear the 
more probable origin of this mass, when we consider its eliemical com- 
position in comparison with tliat of the iron ore, which wc know to 
have been thrown up with the serpentine, occurring on the estate of Mr. 
Whip})lc, and the fact that the ore at Iron Mine Hill is accompanied by 
serpentine mixed with its mass in every part, gives still greater reason 
for this belief." (/. c, pp. 52, 53.) 

Ho gives as the result of his chemical analysis of. the *' Porphyritic 
Iron Ore from Iron Mine Hill, Cumberland," the following {l. <\, p. 53) ; — 

SiOa 23.00 

A1,0, 13.10 

Fc^O, 2 7. GO 

FcO 12.40 

MnO 2.00 

I\IgO 4.00 

TiO^ ir^.30 

H^O and k)ss 2. GO 

Total, 100.00 

vol,, vir. — ISO. 4. 



In 18G9 the Khode Island Society for the Encouragement of Domestic 
Industry jjublishcd a report relating to the coal and iron in Rhode 
Island, from which we glean the following. The iron ore is regarded 
as practically inexhaustible, the mass at Iron Mine Hill visible above 
drainage being estimated at two millions of tons. 

''It is also conceded, as regards quahty, that the Cumberland ore is 
free from sulphur and phosphorus, the most common and worst im- 
purities, and that it contains manganese, the most prized of all the 
elements found in connection with iron. For these reasons the Cumber- 
land ore is sought by manufacturers at a distance, to mix with softer 
ores and improve their quality, and is now exported from this State for 

that purpose." 

It seems that this Iron Mine Hill ore was employed in 1703, mixed 

with the hematite of Cranston, R I., for the casting of cannon. The 
work was done at Cumberland, and, in part at least, '*the cannon used 
in the celebrated Louisburg expedition, In 1745," were cast from those 
ores. The mannfacture was abandoned in 17G3, owing to an explosion 
of the furnace, by which the proprietor was killed. 

During the administration of John Adams the same ores were also 
used for the mannfacture of cannon. It seems that the Cumberland 
(Iron Mine IlilJ) ore -was employed in the manufacture of charcoal iron 
at Easton, Chelmsford, and AYalpole, Mass., as late as 1834. "The 
Cumberland ore, mixed with equal quantities of Cranston hematite or 
bog ore, produced, for a long period, a charcoal iron unsurpassed in this 
country. . . . The Cumberland ore contains an uncertain percentage of 
titanium, wliich, while it improves its quality, helps make it refractory. 
The ore is porphyritic, the magnetic oxide being associated with earthy 
minerals, principally feldspar and serpentine." It would seem that in 
1860, and before, the ore was largely shipped to Pennsylvania to mix 

with other ores. 

A letter of Professor Pw II. Thurston, published in this report, states : 
'' The Cumbcrlaiid iron ore is of the kind known to mineralogists as 
■ 'ilmcnite'; among metallurgists as ' titaniferous magnetic ore,' andiron 
manufacturers, on account of its peculiar value for producing steel, 
would term it a 'steel ore.' . . . The Cumberland ore is conveniently 
located and of inexhaustible extent; it is perfectly free from noxious 
elements, though somewhat refractory; it will furnish a very strong 
iron or a most excellent steel ; it can bo smelted within the State at a 
profit ; it can be made directly into steel at a much greater profit ; steel 
made from it will bring the highest prices in the market." 








umt^ -JOtrZ^'—J^-jK- iV JC -4UZ. VJr_1li Lu_ 

_-ii i_TH ■^-'z^u^.-J:-*-^z.^^^■^.■^ t _imj i ^T\T.-f^.-D 

nn-.TZ- -»-"^^^— "-- -^^-^v r^g-^-iATjTVTw^iTtTWe^c:^^^ ..'"Tx. ?^ 

■ --^ ^1-^ "^ _'- 

-r ^ 1- 



Professor Thurston states tliat the mean of various analyses made of 
tliis ore is about as follows : 





















HjjO and loss 3.05 

Total 100.00 

The ore on one side of the hill, where it has been most extensively 
quarried, shows a dark, somewhat resinous groundmass, holding largo 
striated crystals of feldspar. The resinous lustre and greenish-yellow 
color, as observed under the lens, arc caused by the presence of olivine. 
The olivine becomes more strongly marked on the slightly weathered sur- 
faces seen on the faces of the quarry. Under a lens of high power, the 
olivine shows clearly on the fresh fractures. The olivine in weathering 
decomposes to a ycllo wish and reddish-brown ferruginous powder, leaving 
the other constituent of the rock, the magnetite, well marked. The 
magnetite decomposes more slowly, and forms an incoherent mass after 
the decay of the olivine. The rock gelatinizes with hydrochloric acid, 
and yields a titanium reaction. A fragment allowed to stand a day or 
two in weak hydrochloric acid yielded gelatinous silica copiously. 

A section made with special reference to the feldspar crystals shows 
large porphyritic crystals of the latter enclosed in a mass of magnetite 
and olivine. 

The magnetite forms irregular, more or less connected masses, making 
a sort of sponge-like structure. Its rounded and irregidar cavities are 
filled with olivine, which also occupies the interspaces between the mag- 
netite masses. The olivine Is in rounded forms, which sometimes show 
one or more crystal planes. It is cut through by numerous fissures, that 
usually show a ferruginous staining along their sides. The olivine also 
holds grains of the magnetite. Except the fissuring and ferruginous 
staining, the olivine is comparatively clear, and shows little signs of 

The plagioclase feldspar shows well-marked Hues of cleavage and frac- 



turo, and is somewhat kaolinized along these lines. It contains a few 
irregular flakes of biotite together with grains of olivine and magnetite. 

The order of crystallization appears to have been, first the magnetite^ 
then the ohvine, and lastly the feldspar. 

This rock is similar to the celebrated iron ore of Taberg, Sweden, as 
described by A. Sjiiren in the Geologiska Foreningens Forhandlingar 
(187G, III. 42~G2; sec also Neues Jahrbueh lur Mineralogie, 187G, 
434, 435). The Taberg rock has been worked as an iron ore for over 
three hundred years. This Swedish ore is called by Sjoren " magnetite- 


The feldspar is confined to the peridotite found on one side of the 
hill, where the peridotite passes into a compact greenish-black rock, 
showing patches of serpentine and grains of magnetite. From this fact 
it seems necessary to regard the feklspar as abnormal and local in the 
rock, which in general is composed of ohvine and magnetite or their 

alteration products. 

The structure remains about the same in tlie non~feldspathic portions 
as it is in those before mentioned as holding feldspar. But the olivine 
is entirely changed to a greenish serpentine which shows beautiful 
fibrous polarization. The serpentine retains the form of the ohvine 
grains, their inclusions, and the network of fissures before mentioned. 
In some of the sections considerable carbonate was seen, presumably 
dolomite. In one section part of the olivine grains, especially towai'ds 
their interior, remained unchanged, but on their edges they were altered 
to serpentine. Another change was observed here : the formation of sec- 
ondary crystals of irregular outline that belong probably to actinolite. 
Some are elongated and narrow ; others are short and broad, traversed 
by cleavage planes. They evidently belong to the monoclinic system. 

The origin of this rock could not be told from its field relations, as its 
contact with any other rock could not be found. Since the only method 
in which its origin can be absolutely shown cannot be used without expen- 
sive excavation, it only remains to give the pro))abilities so flir as ascer- 
tainable from the mass itself. Such microscopic characters and mineral 
association have been, so far as wo know, only found in eruptive rocks when 
the origin of such rocks has been studied with sufficient care to determine 
it. Hence we must conclude it is most probable that this mass is erup- 
tive also, until found to be otherwise. 

It closely resembles in structure and composition some of the mete- 

fj; re 

orites, except that its iron is oxidized and not in a native state, 
semblance which for others of the pcridotites has long been pointed out. 



+ w 



It is rocks of this cliaraotor, as has been suggested by others, that give 
lis the most probable clew to the interior composition and structure of 
the cartl). 

The rock in the field shows, to our mind, no signs of structural planes 
that should be referred to sedimentation. On one side the rock is mas- 
sive and jointed, and on the other it is jointed in fine parallel planes. 
This portion of the rock is more Iiighly metamorphosed than the other, 
and, as is usual in highly altered eruptive rocks, joints parallel to cer- 
tain lines of pressure occur. The writer has seen this structure in many 
rocks that were indisputably eruptive, forming wclhmarkcd dikes in 
other rocks. 

A rod away from the main mass of the iron ore, near one end, some 
serpentine appears that cannot be directly coimected with the other peri- 
<lotite. Microscopically its characters and structure are the same as 
the main rock, and there is no reason to regard it as distinct. The rock 
nearest to the pcridotite is a mica schist some hundred feet away. It 
shows no charactei's that would indicate the transition of the ore into it. 

The locality was visited by the writer in October last, in company with 
Professor A. S. Packard, Jr., of Brown University, and Mr. T. S. Eattey, of 
the Friends* School, Providence, R. I. To the latter gentleman I am 
especially indebted for a copy of the paper of the Khode Island Society 
before mentioned, and for other favors. 

This examination may serve as an illustration of the aid that micro- 
scopical lithology may be to the practical side of life, since now, for the 
first time since this rock has been worked, can the ironmaster wlio 
wishes to use it approach iinderstandingly the metallurgical problems it 
presents ; whether he desires to employ the rock as a wliole, or to con- 
centrate the magnetite first. 

CAMnuiDGE, Mass., May 13, 1881. 



- L 


No. 5. — Observations upon the Physical Geography and Geology of 
Mount Ktaadn and the Adjacent District, By C. E. Hamlin. 

The " Geological Map of Northern Maine," that accompanies the 
*' Prclirninary Tlcport upon the Natural History and Geology of the 
State of Maine," for 1861, represents Mount Ktaadn* as included in a 
large granite district, of which it is the culminating height. The area, 
a& delineated, is an ellipse, the axes being respectively about tvvcnt}^ and 
forty mdcs in length, — the major axis running very nearly in a north- 
east and southwest direction. Between the most northerly of the two 
foci and the northeast border of the district, Ktaadu is placed ; while 
between the other focus and the southeast margin are situated the 
" Ebcme Mountains," so called by the compiler of the map. The 
Penobscot Kivcr, in a course intermediate with the two axes and oblique 
to each, crosses the intervening country, which has a general elevation of 
not more than 550 feet above sea level, and is thickly sown with lakes. 

An excursion, of which this paper states results, was made in August 
last, along a route that passes through nearly the whole length of the 
supposed granite area. The special purpose of the writer at the outset 
was to compare the granite of the lower grounds with that of Ktaadn 
itself, which had been partially studied in August, 1879, and less care- 
fully in 18G9 and 1871 ; to fmd, if possible, at some points, the junction 
of the granite with the suiTounding stratified rocks ; and to continue the 
exploration of Ktaadn with reference to completing the model of the 
mountain, of which a heliotype is herewith presented. The route selected 
compriKCH the northern seven miles of Schoodic Lake, fifteen miles of 
forest travel to the Middle Joe Merry Lake, a course through this, the 
Lower Joe Merry, Pemadumcook, and Ambejijis Lakes and their connect- 
ing " throughfates," and nine miles up the Penobscot to the mouth of 
the Aboljacarmcgns Stream, where the ascent of Ktaadu begins. From 
the terminus of highways at Brownsville, the route measures about fifty 
miles in length. 

* The spelling Ktaadn is adopted in accord.ince witli an opinion connnnnicated to 
the writer by J. Haniuiond TrunihuU, of Hartford, the most eminent living authority 
upon Indian dialects. Dr. Jackson, Thorcau, and a few others, have previously used 
the same form. 

VOL. VII. — NO, 5. 






As almost nothing definite is on record respecting the depths of the 
lakes that cover so large a portion of Northern Maine and British Amer- 
ica, soundings as numerous as circumstances permitted were made of the 
lalies traversed. And though the Geological llcports represent the lakes 
above named — except the first; of which no account has appeared in 
print — as enclosed by shores made up of loose material, it was thought 
best, in consideration of the remarkably low stage of water then pi^evail- 
ingj to re-examine the shores and beds of the lakes in regard to their 
composition. The same course was adopted for the Penobscot Iliver, 
especially at the five falls and portages that intervene between Ambe- 
jijis Lake and Aboljacarmegus Stream. 

The Lakes. 

Schoodic* Lake, which shares its name with the larger Schoodic lakes 
that lie on the eastern border of Maine, is in some respects the most 
interesting of all that occur in this region. In his "Water Power of 
Maine," Wells gives its area as sixteen square miles, and it is said to 
have a length of ten miles, and in its central part to be two and a half 
miles wide. It is free from islands, except at a single point upon the 
eastern shore ; and the forest that surrounds it shows no break in its 
continuity, nor any other sign of settlement. The absence of islands 
from the main body of the lake indicated deep water ; but the rough 
condition of the surface, when we boated over it, prevented us from try- 
ing the depth. Our guide, Mr. Clapp, was employed to sound the lake 
on his return, and the list of his numerous and careful soundings shows 
it to be by far the deepest of all the lakes through which our route lay. 
The part over which we passed is enclosed by shores of granitic detritus, 


and there was nowhere to be scon any outcrop of the slates that under- 
lie the whole surrounding district. 

From the Schoodic to the Middle Joe Merry, our way was along a log- 
ger's road through continuous forest, which occupies a land surface very 
level and entirely drift-covered, not one exposure of ledge being observed 
in the whole distance of fifteen miles. 

series of lakes will be apparent from inspection of the accompanying 
map, no more need be said of it than that, flavored in general by ab- 
sence of wind, which, in a brief space of time, raises on these lakes a sea 

Since our course through the 

* The name as applied to this lake is prohal)ly a refinemeTit upon an earlier one, 
found on the older maps, that ot" Skoclum Pond, itself perhaps the coiTuption of 
some now unknown Indian name. 



1 "f^^'Hi^T--^ >:r 

IrrX ii^rk — ■■■■■■■ r L-n— iilLT^" 

_-tkj-_j^ -^ ^ V ^ ."^ '^^TTtT' L i- '^;3»y«ioM-c c 

K ^ij-n^a* ■ JV.' J Sri . I ^ FT"_=t^rt^ i^ "l^i^K^E^Vi **rt*h^fc^^.^K.Tt ^T^ 

■f Oi_ 

, _^^ ^.^..^^^».>__^_^^ _^^,p__^ j« 

-r.— ^. * .V-. -l^■■- r.^^-^-»J-P"_h-.V r TTJ- 



dangcroua to boats, our examinations wcro continued from Pemadumcook 
Lake to the foot of the North Twin, whence, returning to Ambejijis 
Lake, we proceeded up the Penobscot. 

For the first ten days our party consisted of six persons, two boats' 

one made up of my companion in two former trips to Ktaadn, 

crews ; 

Dr. Crosby, of Waterville, Me., his son and nephew ; the other, of Mr. 
L. E. Bhiko, of Worcester, Mr. Ckipp, and myself. In soundini;- lenotli- 
wise of the lakes, our boats often took opposite sides, and, landing fre- 
quently upon the shores and islands, we carefully viewed the unusually 
wide extent of rocky surface laid bare through the long-continued 
drought. Yovy nemiy the sam6 conditions observed in one were found 
to j)rovail in all the other lakes and their connecting streams. All are 
bordered by detrital deposits, constituting occasional sandy or pebbly 
beaches of small extent, but ordinarily made up of granite bowlders 
having angles but little rounded by attrition, and which are often so 
crowded together as to resemble walls. The smaller islands that stud 
the lakes are sometimes banked up on all sides, or wholly covered over, 
■with bowlders that have been borne to their present resting-places by 
the action of ice in successive winters. 

The only occurrence of rock in place, upon any of the lakes and 
throughfares visited, was observed later Tipon the Upper Joe Merry, 
which lay to the west of our route from Sehoodie Lake to the Middle 
Joe Merry. On the return of Dr. Crosby and his companions, at the end 
of ten days, they "carried" from the Middle to tlie Upper Joe Merry, 
which has a length of about three miles. An examination of its mar' 



,^in, made at my request since I was myself to return from Ktaadn by 
the Aroostook route, discovered upon a projecting point a granite ledge, 
which for seventy-five feet forms the shore, rising steep ton feet from tie 
water. The southern half of the lake was crossed, but, with the excep- 
tion named, only shores of drift were seen. Soundings were at the 
same time taken, which will be given in the tables of depths. 

Ambejijis Lake, ui^permost of the scries of expansions of the Penob- 
scot known as the Pemadumcook chain of lakes, and but two miles long 
by three fourths of a mile wide, receiving directly whatever of detritus 
is swept down by the rapid river above, might be exj^ccted to be shal- 
lower than the rest. It proved, however, to be deeper than the average 
of the others, and here at one place was made the deepest sounding, 511 
feet, that occurred in the series. This lake was once a connecting link 
between Pemadumcook and the larger Millinoket Lake on the east, 
which, according to Wells, has an area of eighteen square miles, while to 



Pemadumcook, including Ambejijis, is assigned an extent of sixteen 
square miles. The whole constituted one lake with two outlets, a case 
rare in Maine. The formerly connected lakes are now separated by 
a wide lagoon and a bush-grown sand-flat of four rods wide, products of 
detritus brought down by the river. In times of flood, boats still pass 
freely from one to the other. Millinoket at present has for its outlet a 
stream bearing the same name as the lake, which, rising from the east- 
ern end, flows south into Shad Pond, the lowest lake-like expansion of the 
Penobscot. The lagoon, through which in 1871 we wore barely able to 
thrust our light boats, was now a broad surface of mud, impassable by 
boat or on foot, and an eff'ectual barrier to the extension of our sound- 
ings and exploration into Millinoket. That this lake, as to its surround- 
ings, is not unlike the neighboring ones, we arc confident from our 
recollections of a pretty careful examination of it made in the previous 
visit. They agree with the statement of Dr. Jackson, that " the islands 
are composed of the detritus of granite rocks, and the shores are com- 

posed of the same materials. 

" * 

Seen from the summit of Ktaadn, the 

outspread Millinoket presents in a marked degree those flowing outHnes 
of gently rounded bays which distinguish lakes enclosed by detritus 
from the angular, irregular, and often narrow recesses that arc said to 
characterize lake basins excavated in solid rock. Of the latter class I 
know not an instance in Maine. 

The following tables register soundings made at intervals in what 
appeared to be the deepest parts of the lakes we navigated. Casts were 
made from the two boats, running some distance apart, and commonly in 
nearly parallel lines. The columns marked A contain the results of 
soundings taken by myself, with the assistance of Mr. Blake. The col- 
umns B give soundings made by Mr. C. B. Wilson from Dr. Crosby's 
boat. The figures show that the lakes represented, with the notable 
exception of Schoodic, have bottoms that are generally flat; and noting 
the nature of the materials that compose the shores, the lake beds would 
seem to be hollows, which had their origin in irregular accumulations of 
drift deposited on broad, fiattish surfaces.f 

* Second lleport on Geology of Public Lands, 1838, p. 11. 

t G. W. Taylor, Esq., a resident of Cazenovia, Madison County, N. Y., writes as 
follows respecting Cazenovia Lalce, which is one of the feeders of the Erie Canal, and 
situated in a valley surrounded by hills : — " Mr. Ledyard, one of the old inliabiUm ts, 
made many soundings before I came here to reside. The bed of the lake [four miles 
long by three fourths of a mile wide] is as level as a valley ; about one third of its 
area varies in depth only from 43 to 46 feet, — the latter being the greatest d<;pth. 
The south end [the foot] of the lake is quite shallow." 

->-^rf, -u-j ^,.^^__- 

-in—. --^T-^Tt-S" 

-J ■ > iD^^ ■ l' " ■ 7?-v^ . H_^ V3P-wr-*.\— 

-^VT-zr- -■'a* -IT-"-' 'jf^-?-- T-rTTrr 

hk^*-^i Lr*i"Frw i---"r 

-"Lr^c^ir?ini??-E=KI-CiP&\^^^rk.^^rf -i:^^iJfrS^-tiJ"JSai'l^«t33^.rM^:7^ir^ 

^ _ 

^ n 

M - V M „ ^ ^-^^i^,^t^^__ j_>^^_,^^j-j.r™jTi^^^^^_^,.^-t;^ ^Kri^^:^^^w^:s^Jii^*iitr;t^l■fr^JInl. 

n»»tel£;^JTrfc7=^i:jrr^:tj-^^^,Tli^-^-:-t V^T-'.-^^ZT' 




I. Upper Joe Merry Lai 

Off east Rliorc, from middle of that J 
shore to south end of lake 

South of South Ishvnd . 

North of South Island . 

East of South Island . 


2 . 

4 . 


6 . 



10 . 
12 . 

, 17 

West of South Island . . . . J 18 . 


20 . 

24 . 


Up centre of lake from south end \ 27 

















11. Middle Joe Merry Lahe. 

Kunning along central part from lagoon on south to vicinity of outlet at north. 









VOT-. vn. 




























































III. Lower Joe Merry Lake. 

From entrance on south, along middle 1| miles to northwest, till stopped from 
sounding by wind. 















































IV. Pemadumcoolc Lalce. 

Running southeast toward foot, west of middle. Soundings began off small island 
near mouth of Lower Joe Merry outlet, and eontinucd 2j miles down, till stopjicd by 






































« « ■ « I 

i * • ■ 

« # « 4 

• • t « 






From foot, cast of middle, in northwest course, about four miles, nearly to Gull Kock 
on cast shore, opposite mouth of Lower Joe Merry outlet. 









t 4 4 

* # i # 

4 I * 

V « i 

4 4* 

4 i 4 

* 4 4 

4 ^ k 

















V. Amhejijis Lake. 
Along middle, from foot, north to head, about two miles, 






















• • « * t 
■ • • > 

* 1 t 

* • » 






Cast 12 was quite distant from H, and near entrance of Penobscot into lake. 

VI. Schoodic Lake. 

Numbers 1 to 25 give soundings from south end north, along course of west sliore, 
but well out from it ; 26 to 38 were taken oif east sliore, going from south to north ; 
39 to 50 are soundings made in March, 1881, through holes- cut in ice along centre of 
lake, from south to north, at intervals of half a mile. Taken by Mr. Isaac Clapp, wlio 
speaks of his soundings as showing that " there is a mound near the centre of the lake 
105 feet high," above the adjacent deepest parts. 

^ I 




At north end 



















































































VII. Forth Twin Lake. 

Soundings taken by Mr. Wilson, along middle, from north to south, about two miles. 

Mine were lost. 

m. In. 

1 19 

2 18 3 

3 . . 16 

4 22 4 

5 23 

6 22 4 

7 19 6 

8 19 



An Unreported Kame. 

From a spot on the western shore of Middle Joe Merry Lake, known 
to the guide as Gordou's Landini^, a name derived from former lum- 
bering operations, a " horseback," or kame, runs two and a half miles 
north 28^ we>st, forming for some distance the shore of the lake. On 
examination it proved to be an interesting specimen of its kind. It 
slopes at each end gradually to the general level, but through all the 
central portion maintains a tolerably uniform height. At a fairly rep- 
resentative point, it was found to have at its slightly rounded top a 
width of 15 feet, and by use of a clinometer and level the inclination of 
the east side was ascertained to be 30^, and the height 39 feet above 
the lake. The west side has an angle of 25° and rises 2G feet above an 
old pond of equal length with the kame, now changed to a swamp, only 
the width of the kame intervening between the swamp and the lake. 


Many granite bowlders of from one to two feet or more In diaioeter arc 
strewn upon the ridge at and near its summit. The smooth and un- 
broken surfiice of the kame seems to indicate rather that they were 
deposited upon the ridge subsequently to its formation, than that, having 
made part of the original structure, they were by denudation left pro- 
jecting from Its surface. 

The Granite Area. 

Doubts respecting the actual existence of the granite area represented 
in the geological map were suggested during a rapid passage, in 1869, 
over the route now taken. The facts already stated, so far as they bear 
on the theory of such an area, do not go to sustain it. The observations 
now to be noted are more closely related to it. 

From Gordon's Landing an excursion was made to Joe Merry Moun- 




tain, which is situated well within the limits of the supposed granite 
district, and is nearest and highest of the elevations that lie west from 
the chain of lakes. Showing upon its sides, as it docs, bare cliffs through 
the forest that covers it, this mountain was chosen as a locality where 
wo might hope to fmd some evidence of the nature of the rock underly- 
ing the vicinity, which, at the lower levels, had been hitherto concealed 
by thick drift deposits. 

Dr. Jackson, while on his way to Ktaadn in 1837, saw this mountain 
from the shore of Ambejijis Lake, and describes it in these words : 
" From this spot I took a view of Joe Merry Mountain, which appears 

rising to a considerable elevation on the southwest It is composed 

of granite, and is a commanding point of view for examining the sur- 
rounding country, so that it is frequented by explorers for timl)er." * 
But as Jackson was never nearer to it than when he ran down Pema- 
dumcook Lake on the return from Ktaadn, it is evident that this 
statement rests merely on report. 

A circuit of seven miles through the woods brought us to the foot of 
the mountain on its north side, where it rises at a sharp angle from 
the valley. For the last four miles of our way up to this point, the 
ground was thickly strewn with granite bowlders, which became larger 
and more numerous as we approached the mountain. So far neither 
rock in place, nor bowlders of other material than granite, had any- 
where been seen. But, 200 feet up from the foot of the steep north- 
ern face, we began to find mingled with the granite bowlders others 
of considerably altered mica schist. At the height of 450 feet, and 
again at 600 feet, above the base, we came upon exposed ledges of rock, 
the siunc in kind as tlTo newly found bowlders. So far the ascent 
had boon abrupt. For the next hour it was more gradual, and 
several small levels and depressions were traversed. Latci', a narrow 
and deep ravine was crossed, having on its farther side a cliff of schist, 
similar to that observed below, which rose at an angle of 35"^, and so 
high as to require twenty minutes* sharp climbing to gain its top. 
Thence a gentle ascent was followed for ten minutes, when an elevation 
was attained of 1,G35 feet above the lake, rw determined by means of an 
aneroid, whose readings at various points were compared with simultane- 
ous observations made by Mr. Blake with a Green's mountain barometer 
stationed in camp at Gordon^s Landing. At this height numerous gran- 
ite bowlders were still scattered over the mountain top. The mountain 
is a long ridge, running north and south. Its actual summit now lay 

* Second Report on Geology of Public Liiiula, p. 13. 



perhaps half a mile before us, hut scarcely more than 150 feet higher 
than the point already reached. As it was covered with forest, and 
promised neither outlook nor further revelation of the lithology of the 
mountain, and as our time was exhausted, we advanced no farther, hut 

returned to the lake. 

From the head of Ainbcjijis Lake, the route to Ktaadn for the next 
nine miles follows the Penobscot. For this distance, and in fact all the 
way from Shad Pond, below, to Chesuncook Lake, the river at short 
intervals widens into still lakes connected by rapid, rocky, and narrow 
reaches of running stream. As related to the falls and rapids, eacli of 
the numerous lalicdike exjjansions is styled by rivermen a " dead-water." 
These remaining nine miles of water route include five falls, requiring as 
many portages of from twenty to ninety rods in length, each fall having 
below a dead-water bearing the same name as the fall itself. Thus 
Ambojijis Lake is the dead-water that lies below Ambejijis Falls. 

While the prevailing and excessive drought greatly retarded travel 
upon the river, it afforded an unecpialled opportunity to learn the nature 
of its bed, now bare to an extent unknown before for many years. One's 
conclusions with regard to the geology of the district south of Ktaadn 
must be shaped largely by the view he takes of the facts that relate to 
the nine miles of river bed here referred to. And since the previously 
recorded examinations of this part of the river were made in haste, and 
at times when high water in great measure hid the channel from obser- 
vation, it seems best to state the very simple facts somewhat in detail. 

Ambejijis and Passamagamet Falls, first in order, and a mile and a 
half apart, are caused by accumulations of large granite bowlders that 
choke up the narrow channel and give origin to the dead-waters next 
above them. To remove the bowlders would be to draw off the waters 
of those pond-like expansions. Not a trace of rock in place could be dis- 
covered in the river bed at either of these falls, nor upon the adjacent 
shores, which are elevated but a few feet above the level of the river. 

The first ledge that appears upon the river or its expansions, from the 
foot of Noi'th Twin Lake northward, occurs twenty rods below the third, 
or Katepskonegan Falls, longest of the series, stretching seventy rods 
along the course of the river. The ledge, which is of granite, rises on 
the eastern shore directly from the water in a precipitous head of twenty 
feet in height. Northward to the falls, the east shore is a steep exten- 
sion of the head, which inclines downward to the north, till at the falls 
themselves the ledge is to be seen only on the floor of the river bed. 
There is no exposure of granite upon the western side to match the high 




head upon the casteni ; neither could rock in pkce be detected in tlie 
low banks of drift abreast the falls, nor along the carry. In the chan- 
nel at the foot of the falls, the ledge was mostly hidden by accnninlated 
granite bowlders, wdiile at the upper part the water was seen to pitch 
over successive shelves of granite in place. 

Though it was hero that we first came upon fixed rock in the river 
bottom or banks, we had seen, half-way between this and the next tall 
below and some distance back from the west shore, two high forest-cov- 
ered hills, wliich were the first considerable elevations met with since 
wo left the lakes below. On the southern slope of each hill is a naked 
clilf. Circumstances rendered it impossible to land and push through 
the woods for a visit to the cliffs; and no second view of them occurred, 
since my return from the region took place by another route. 

The passage through the dead-water of more than two miles to the 
fourth lull showed no trace of rock in place, cither in the channel or along 
the shores. Nor did the neighboring low hills exhibit any faces of 
exposed rock. 

Pockwockamus Falls, the fourth, occupy about twenty rods of the riv- 
er's length, beginning abruptly from still water above, and ending as 
abruptly below in water of like character. The bed is an uneven floor 
of granite ledge, measurably free from bowlders in the middle third, 
but on cacli side covered with large blocks, mainly riven from the under- 
lying fixed rock, which docs not differ materially from that of the third 

At the fifth or Aboljacarmegus Falls, a mile above the fourth, is the 
next exposure of rock m situ. Tlic river makes here a sudden bend, 
flowing from northeast to southwest, and is exceedingly narrow. The 
lengt.h of the fall is ten or twelve rods only, and the underlying granite 
differs strikingly from that of the third and fourth falls, and from that 
wliich makes up Ktaadn. In places it is highly porphyritic, and occa- 
sional patches of several square feet consist of massive feldspar or quartz, 
not constituting veins. At the tliird and fourth falls the granite, being 
highly jointed, has become divided into rhombohedral blocks of all sizes. 
Worn at the angles in various degrees by attrition, these make a large 
proportion of the bowlders that at both those falls conceal the rock in 
place over much of its area. At the fifth fall the fragments split from the 
solid mass in somewhat lenticular forms, never in rhombohedral blocks. 
About the foot, the only pot-holes anywhere seen occur in considerable 
number, but not of great size. Their presence here and absence from 
the falls below must be explained by difference in the texture of the 




rock at the localities, rather than by difFcrcnce of other conditions. 
Along the portage past this fall are several small exposures of granite 
ledge, the only ones that were seen near the river, apart from its bed or 


The granite of the three ledge-formed falls, as "well as that of Ktaadn, 

beyond any other that I have elsewhere seen, is free from veins and 
dikes. In fact the only instances observed of either in the whole 
region were a quartzose vein, an inch wide, that ran through a block 
twenty feet in length, evidently torn from the rock on which it rested at 
the fourth fall; and a small trap dike, four inches wide, that traversed 
a nearly buried erratic bowlder lying on the portage at the fifth fall. 

Another circumstance common to the granite of the several localities 
is, that at the falls only is it visible. Above and below each fall the rock 
so suddenly and entirely disappears, that over the spaces between the 
falls granite in place could nowhere be discovered. It would seem, then, 
that at the third, fourth, and fifth falls a ridge of granite in each case 
cuts the river bottom transversely, damming the stream and obliging it in 
its course seaward to tumble in a fall over the lower slope of the ridge. 
The underlying fixed rock which intervenes between the granite ridges 
is so hidden by drift deposits that nothing can be asserted positively 
concerning its nature. One would naturally suppose it to be granite; 
but without attaching much importance to the marked difference between 
the rock of the upper fall and that of the two next below, there are other 
considerations, to be noticed presently, which suggest a doubt whether 
the three ridges that occasion the three ledge-formed falls have any lat- 
eral connection below the drift, and the question whether they may not 
be distinct ridges of intrusive rock, thrust up through strata from a com- 
mon source beneath. 

The theory that the district south of Ktaadn is part of a continuous 
granite region, is a hasty generalization from insufficient data, origi- 
nally made by Dr. Jackson. Prof. Hitchcock, in his survey, which was 
discontinued at the close of its second year, made no personal examina- 
tion of the Penobscot valley between Chesuncook Lake and Grand 
Falls. He therefore naturally adopted in the construction of his geo- 
logical map Dr. Jackson's view of that district, supplemented by some tes- 
timony of one of his own assistants. The map was of course intended to 
be provisional only, and, had the survey been continued, would probably 
have been superseded by others. All the basis that exists for belief in a 
wide granite area south of Ktaadn is found in a few passages of Jack- 


8on*s and Hitchcock's Reports. They can here be presented in small 






Jackson's notes of his trip to Ktaadn contain only the following brief 
statements respecting the rocks m situ which he saw on the waylo and 
from the mountain. First, the one previously quoted in full, that Joe 
Merry Mountain "is composed of granite."* Second, that, "leaving our 
boats, we walked to Pock-wockamus Falls, where the river rushes over a 
ledge of granite." f Third, " All the rocks at Quakish Lake t are 
granite, and the water falls over huge bowlders of that rock/' § 

Dr. Jackson's assistant, Mr. J. T. Hodge, had preceded him by three 
months in the passage up the river. He speaks of but one of the two 
hills I have described as lying west of Katcpskonegan Dead-water, 
saying: ''On its western side is a high' hill of granite, covered with 
immense loose blocks of the same rock, piled one upon the other almost 
perpcndiyulaj-Iy." He adds: "Two miles above [a fall over "loose 
granite rocks"], we were obliged to carry by again on the western side. 
The opposite bank is formed of granite .... lying in the best position 
and form for working." Continuing, he remarks: "Not far above 
this wc arrived at a fifth portage, which is called the Pauquakaraus [in 
fact Aboljacarmegus]. .... At the head of this portage, the bank is a 
smooth ledge of granite." (| 

Mr. J. C. Houghton, who for the year 18G1 was Hitchcock's assistant, 
furnished for his report the following facts. In the account of a trip 
from Moosehead Lake down the Penobscot to Ktaadn and beyond, he 
notes that at the fourth and fifth portages " the river falls over ledges 
of fine granite." ir Respecting the fixed rocks upon the river and lakes 
below, ho makes no further remark than tliat " near the outlet of North 
Twin Lake is the southeast limit of the granite, and the quartz rock 
[which he had last seen between Chcsuncook and Eipogenus Lakes] 
again appears " "^^ 

Elsewhere Mr. Houghton mingles facts and conjectures. Having vis- 
ited the " Katahdin Iron Works," ft which are situated in the township 
that corners upon Brownsville at the northwest, he proceeded twelve 

* Second Report on Geology of Public Lands, p. 11. 
t Ibid., p. 14. 

t Quakiah Lake on Hitchcock's map is placed ontsidc of the ginnite district, the 
last granite in place being now known to occur a little below North Twin Lake, Ibove 

§ Ibid., p. 20. II Ibid., p. 63. 

IF Prel. Eep. Nat. Hist, and Geol. of Maine, p. 440. 
** Ibi<l., p. 440. 

ft A confusing misnomer, since they arc situated full thirty miles in a straight hne ■ 
from the mountain whose name they bear. 




miles farther northwest to a remarkable gorge, known as the "Gulf." 
This has been eut by Pleasant lUver for five miles through black slate 
that rises on either side in walls, sometimes to the height of from 100 
to 300 feet, often vertical or overhanging. 

He next '* ascended Saddle Eock, a mountain wdiich is about eight 
miles north 36° east from the Iron Works."* Its height he gives as 
*' 3,010 feet, being 2,416 feet above the ground in front of the furnace 
of the Iron Works." f He says again : '^ 1 was disappointed when I got 
to the summit to find it composed of the same slate formation that I 
had been on so long." After a few lines more he adds : " To the north- 
west arc several mountains, the highest of which is called ' White Cap/ 
on account of its naked white summit, which, as a hunter informed mo, 
is composed of granite. It is about eight or ten miles from Saddle 
Eock, and is probably near the southwest limit of the Katahdin granite 

region." :[ 

This report of a '' hunter," and Dr. 'Jackson's false statement, grounded 
on hearsay, that Joe Merry Mountain is made up of granite, constituted 
Mr. Houghton's only warrant for considering the granite district to 
extend beyond the Pemadumcook chain of hikes, and so far south as the 
northern line of the township next north of Prownsville, as is repre- 
sented upon the geological map. Furthermore, the fact that, in the 
whole forty miles of the route between Ktaadn and the imaginary south- 
ern line of the district, granite has been found coming to the surface, 
over exceedingly narrow areas, in five localities, — viz. at the third, fourth, 
and fifth falls, near the outlet of North Twin Lake, and at the Upper 
Joe Merry Lake, — furnishes a very slender basis for belief in the exist- 
ence of a continuous granite area south of Ktaadn. 

Suppose we concede to be made up of granite the cliffs seen by Mr. 
Hodge and myself on the hill, or hills, west of Katcpskonegan Dead-water, 
and apparently identified by him as granite through a distant view 
gained as he passed up the river in his boat.; and White Cap, reported 
to consist of granite by one whom we do not know to have learned its 
character from examination. With these additions we have 
data still entirely insufticicnt to justify the conclusion that has been 
drawn from them. 

The sudden appearance, and as sudden disappearance, of granite in 
districts covered by stratified rocks, arc characteristic of Central Maine. 
The granite not uncommonly occurs as isolated hills separated by a 

* Prel. Rep, Kat. Hist, and Gcol. of Maine, p. 430. 

t Ibid., p. 430. X Ibid., p. 431. 



greater or less extent — sometimes by a score of miles — of imbrokeu 
strata. The same reasoning that wonld make the district sonth of 
KtaaJo a continuous granite area, would apply as well to others known 
to be underlaid by strata through which granite shows itself in detached 
hills or ridu'cs. 

The case of Augusta, situated near, but not at, the southern border of 
the region of slates and schists, is instructive in this connection. The 
conclusion wliich even a geologist looking over that vicinity in haste might 
feel to be the natural inference from obvious and abundant data, would 
nevertheless be a wholly false one. An outline of the case only can here 
be given. Augusta city is built on both sides of Kennebec River, upon 
well-developed terraces which form the sides of a valley that has there 
been excavated to the depth of 300 feet below the level of the adjacent 
country. The width of the valley cast and west, from snnnnit to sum- 
mit, is a little over one mile in a straight line, and midway runs the 
river in a course somewhat west of south. The terraces and suftimits 
on either side are composed of drift deposits, so thick that the deepest 
wells nowhere reach solid rock ; and four sharp ravines, that on the 
western side cut the terraces down to the level of the river at their 
mouths, have bottoms and sides of drift, as has the river bed, except at 
two points. The highest part of the western summit is a "granite" 
ledge which rises in a knob some thirty feet above the rest of the sum- 
mit and the general level of the country. Its top has an area of not 
more than one or two acres, and falls off rapidly on the north, east, and 
southeast beneath the enveloping drift. A mile south of this point, and 
half a mile southwest from the State House, is a broad hill, about 400 
feet in height above the river. On its soutliwest side, which lies in 
ILillowell, are the quarries that furnish the well-known *'Halloweil 
granite." The hill throughout is a solid mass of the same material. 
In riding out of town two miles to the west, northwest, or northeast, one 
comes upon several "granite" quarries in each direction. In view of 
the foregoing facts, a visitor woxdd feel himself justified, if no further 
examination were made, to pronounce "granite" to be the underlying 
rock of the vicinity. But should he notice just across the railway track 
from the station, at the foot of the second terrace, forty feet above the 
i-iver and 200 feet from it, an exposure of rock now mostly hidden l)y 
n, granite bank-wall, he woultl find it to consist of hardened, upturned 
schist; and in the drought of summer he would see in the river i)ed, 
for a few rods above and below the railway bridge, ledges of the same , 








Across the deep, narrow valley of a tributary to the Kennebec, above 
half a mile in an air-line northeast from the granite knob before men- 
tioned, and at the northern limit of the city proper, rises more than 300 
feet above the river what was formerly known as the Andros Hill, the 
upper part of the so-called Cushnoc Heights. On the southeastern slope 
of its upper hundred feet, on nearly the same level with the road, but on 
the opposite side of that part of the hill, and so hidden from the view 
of the passer-by, is an abandoned quarry of mica schist. Here, too, the 
rock plunges off on the south, east, and west beneath an unknown depth 
of drift.* 

Finally, should the observer examine, for the four miles that intervene 
between Andros Hill and the northern line of the township of Augusta, 
the very few exposures of rock in place that occur along the river road 
on the west side of the Kennebec, and upon the farms crossed by the 
road, he would find in every case schist, and that only. Upon the cor- 
responding road cast of the river, only schist is found for the whole six 
miles of its length across the township. It is evident, then, that the 
underlying rock of Augusta is the upturned schist, which becomes at 
Waterville, eighteen miles north of Augusta, the almost vertically placed 
Taconic or Lower Silurian slate that stretches to Moosehcad Lake on 
the north, and easterly to and beyond the city of St. John, N. B. 

In the great denudation which tliis extensive region has undergone, 
the more resisting granites f of Kennebec County have been left project- 
ing as hills above the softer schists, which, worn down to lower levels, 
have been covered with deposits of drift, frequently of great thickness. 
For miles these lower grounds and the hills also may be traversed with- 
out meeting any indication of the nature of the underlying rock. Thus, 
upon the road along the western side of the Kennebec, between Andros 

* Half a mile above the bridge, at tbe foot of Cushnoc Heights, is the Kennebec 
Dam. In 1839 a freshet swept away seven acres of "land at the west end of the dam, 
and cut a new channel for the river 500 feet in width, the floor of which, when the 
waters abated, was found to be a transverse ridge of well-marked mica schist. In 
extending the dam across the new channel, the rock thus laid bare was soon after 

hidden again from view. 

t The so-called granite of Hallowell and Augusta was termed by Jackson " granite 
gneiss" (B"'irst Rep. Geol. of Maine, p. 83), and is declared by Dr. T. Sterry Hunt to 
be " true gneiss " {Am. Jour. Sci., [3.] T. p. 85). But is the sudden transition, in so 
many places within a small area, from crystalline rock to distinct schists, compatible 
with ti.e idea that the former is a metamorphosed portion of the latter ? Are not the 
relations of the two more consistent witli the hypothesis that the "gneiss " is in real- 
ity eruptive granite, which in its paasage through the strata has changed the original 
slates into hardened schists ? 




Hill in Augusta and Watcrville, I remember but five small spots where 
ock in situ rises to the surface. Upon the adjoining flirms a few others 
may be observed. All are little patches of outcropping strata. Goin'^ 
nortliward from Augusta, wherever the strata are harder tlian usual 
they rise into hills. At Watcrville, while fissile slates occupy the low 
grounds, they lose the slaty structure and pass into hard schists in sev- 
ei-al high hills, one of which presents a bold, precipitous face. The 
numerical proportion of such hills increases farther north, tdl, south and 
cast of Mooschcad Lake, so far as examination has been made, hills and 
mountains of schist far outnumber those comjiosed of granite. Isolated 
granite lulls occasionally rise in districts of slates and schists, but 
nowhere is anything to be found that can be termed a granite district. 
Judging from the foregoing facts and instances, we must think, until 
stronger proof to the contrary is produced than at present appears, that 
the country south of Ktaadn, to and beyond the Joe Merry Lakes, is 
part of the great region of stratified rocks which surrounds it on all sides. 
On such an hypothesis, the presence of Joe Merry Mountain where it is 
a mass of schist — is comprehensible; but how shall it be accounted for 
if supposed to ris^ out of a granite district 1 

On arriving at the mouth of the stream where the trail from the river 
to the summit of Ktaadn begins, it had been my purpose, before making 
the ascent of the mountain, to run up the Penobscot twelve miles far- 
ther, to Ripogenus Portage, upon which occurs the border line between 
the granite and the stratified rocks in that direction. But lack of water 
in the river, and its obstruction by great gatherings of logs, formidable 
enough below and known to be worse above, made further boating 

impracticable. The Ilipogcnus trip was therefore unwillingly relin- 

Of the northwestern portion of the so-called granite district, T can 
speak, then, only from notes and recollections of a canoe excursion made 
in 1871 from Mooschcad Lake downward. They enable me to say, how- 
ever, that the river's course, from the Ripogenus Gorge to Sourdnahunk 
Falls, lies chiefly among hills. Those on the north skirt closely the 
left bank of the river, and arc foot-hills of the Sourdnahunk Mountains, 
which are a little beyond. The hills are frequently precipitous, present- 
ing a frontage of granite cliffs. Except at the Ambajcmackomus Falls, 
where the river plunges eight or ten feet over a shelf of granite, I have 
no distinct remembrance of ledges in the channel, which is thickly 
strewn with granite bowlders. But the character of the heights adja- 
cent upon the left leaves no room for doubt that, between the limits 




Specified, the reuobscot flows over underlying granite, superficial or 


Mount Ktaadn, as we shall see, is composed wholly of granite, and its 


relation to the Sourdnahunk Mountains, which extend from Ktaadn 
westerly ten miles, is such that it and they must be regarded as parts of 
one continuous range. It cannot be doubted, therefore, that a Ktaadn 
granite area" exists, having for its length that of this range, and 
including on its southern side the channel of the Penobscot, at least so 
far down as Sourdnahunk Falls, which are three miles above the mouth 
of Aboljacarmegus Stream. These statements arc confirmed by the few 
observations upon this part of the river which the Geological Ecports 


The floor of the Great Basin of Ktaadn has an elevation of 2,000 feet 
above the sea. As one goes outward from it by the present route to the 
East Branch of the Penobscot, better styled the Mattagamon River, he 
skirts along the northern foot of the abrupt portion of the eastern moun- 
tain. On leaving that, he quits the last trace of rock m sita, which 
nowhere reappears in the descent of more than 2,400 feet made along the 
twenty-three miles of way to the crossing of the Mattagamon at the 
Hunt Place. There is abundant testimony that ledges do not come to 
the surface on the old Keep Path, which diverges from the present route 
at Ktaadn Lake and runs seven miles to the foot of the Eayt Slide. 
It is certain, then, that on the east side of Ktaadn granite has not 
been discovered upon the gradual lower slopes of the mountain, which 
make up nearly half of its whole height. It is certain, too, that just 
beyond the western or Sourdnahunk end of the range, the granite dis- 
appears beneath the surface. To the south of the Sourdnahunk Moun- 
tains, as we have seen, granite without doubt makes up the river channel ; 
but the aspect of the low country to the south warrjuits the suppositioii 
that granite as> superficial rock extends in that direction not far beyond 
the Penobscot. It seems, therefore, in the highest degree probable, that 
the Ktaadn "granite area" includes little but the mountains them- 
selves, and that, nowhere extending far out from the foot of the range, it 
does not, in some parts, embrace even the lowest slopes. 

Mount Ktaadn. 

The low country south of Ktaadn has an average elevation of not 
more than f)50 feet above the sea. From it rises the mountain by mod- 
erate gradations to less than half its altitude, or about 2,1^00 fetst on 



the south side, but the uppci portion, rearing itself 3,000 feet higher, is 
bounded by dccUvitiow of great abruptness. 

A brief description, ilhistratcd by the accompanying heliotype of a 
model wliich represents the upper tiirce thousand feet of the moinitain, 
will render intelligible subsequent references to the general features of 

The crest that bears the higliest peaks is bent lil^e a deep crescent, 
opening north, and enclosing the Great Basin. At the centre of the 
crescent are the two chief peaks, which differ in altitude less than 
twenty feet, and are not more tlian a third of a mile apart. Directly 
beneatli the East Peak, shoots off to tlie southeast the lonirest of all the 
s}nu-s, which, narrow above, widens greatly towards its foot. Beyond 
the peaks, the eastern horn of the crescent includes a thin, serrated 
crest, and forms at its tip, first, the little towerdike peak known as 
the Chinmey, and then, across a narrow, s([uare-cut notch, the peak of 
Pamola,* named from the Indians' demon of the moiuitaiu. It is known 
to many only as First Peak, so styled because it was tlie first summit 
rca(;hed by tourists who followed the original eastern route to the 
mountain. Pamela has a regularly convex, wide northern face, that 
runs down with a precipitous foot to the level of the basin floor, nearly 
2,300 feet below the higliest peak. Eastward from Pamela projects a 
narrow, sharp-ridged spur, the *' Horseback," — an unfortunate name as 
here applied, since in other cases it invariably means, in Maine, a kame, 
with which this buttress of solid rock has nothing in conn-uon. Towards 
its extremity, the ''Horseback" forks, and sends off to the nortiieast a 

lower, flatdjackod spur, while on its southern flank is the East Slide, 

the smaller oi' the two great slides that arc among the peculiar features 
of Ktaadn. 

Against tlie western horn of the crescent abuts the Table Land, an 
ahnost absolutely plane surface, inclined to the noithwest at an angle 
t)f from five to seven degrees, and liaving a length of a mile and a 
half, and an area of more than five hundred acres. The centre of this 
plateau is a few hundred feet lower than tlie higliest peak, which has an 
elevation of 5,215 feet, as determined by Prof. Eernald. Half a mile 
below the middle point of the sharp brow that bounds the Tabic 
Land on the south is the head of the Southwest Slide. This slide is 

* Till! naino ns given b}' Jacksuu and Uiose, who havo followed him is Fomo'a. 
I hiivc ehosen tho form Pamola on the antliorjiy of Kev. Kugene Vetromilc ("The 
Abi#;ilds and Uieir History," pp. (33-07), foi' many yeary Cailiolic missionary among 
the Indians of iMaine and New Brnnswiek. Dr. De Laski, in a ])aper to be I'eferred 
to liiribcr on, a]i]ili(',s the name ineorreetiy tt) tho " apex of Katalidin." 








the track of an enormous avalanche, which, in 1816,* swept over a course 
of not less than four miles in length. A mile or more of the lower part 
is now wholly grown up to forovst, hut the upper part, for a mile and 
three fourtha, is still covered with loose fragments of rock and gravel, 
upon which vegetation has not encroached, except along the sides. The 

East Slide is less than a mile long. 

The Tahle Land narrows on the west, and sends off a sliarp-ridged 
spur that curves to the southwest. From West Peak there is a descent 
northward and westward, into which the Tahle Land merges, down 
to the level of 4,250 feet, — the lowest part of the central mountain, 
termed the Saddle. Northward from this rises rattier gradually a 
rounded summit 450 feet higher than the Saddle, or 4,700 feet above 
the sea, and 515 feet lower than West Peak. Three fourths of a mile 
farther northeast is a second summit, similar to the first, but slightly 
lower, the two being separated by a moderate depression of tlic ridge. 
A half-mde farther, in tlie same direction, follows a tliird rounded sum- 
mit, perhaps seventy-five feet lower than the first. From the first and 
second ziorthern summits run eastward two sharp and narrow spurs, 
which include the iNorth Basin, so named to distinguish it from the Great 
or South Easin. The northern face of this smaller basin is made up of 
cliffs for the most part nearly vertical. From the second summit runs 
west another long and flat-topped spur.* 

Beyond the Saddle, the mountain stretches some seven miles to the 
northeast, and terminates in a knot of lower spurs, having in the main 

flattish tops and precipitous sides. 

The Great Basin, in its whole extent, forms an amphitheatre, which, 
seen from above, strongly resembles an old volcanic crater. In the ab- 
sence of trigonometrical measurements, its dimensions cannot be accu- 
rately stated ; but they may be approximately given as from summit to 
summit east and west two and a half miles, by a mile and a half from 
north to soutli. Its most precipitous part, tlie southern lobe, measures 
from its head to the Basin Pond about three fourths of a mile, and its 
width is nearly the same. The smaller North Basin approaches in 
shape the capital letter U, and is about a mile and a half long and half 
as wide, fronting a little south of east. The larger basin has a narrow 
gateway opening to the northeast. 

* Williamsou's History of Maine, Vol. I. p. 90. 

t In photograpliiiig the model, light fell upon the western spurs exactly in the 
direction of their liiiigtli. Flooded thus with light, these jtarts have not enough of 
shade to render them distinct. 





The wall of the Great Basin rises highest above its floor on the south, 
becoming gradually lower ou the cast and west sides. The height of 
West Peak above the Basin Pond, as determined by the mean of six 
pairs of simultaneous observations taken with a Crcen's mountain ba- 
rometer at the level of the pond, and with an aneroid upon the peak, 
was found to be 2,287 feet, which is the depth of the basin, measured 
downward fi'om the top of the same peak. Its walls ou the south and 
east are so steep that they have never been climbed, except at one or 
two points, as an act of foolhardy daring. The height of Pamola above 
the little pond, as estimated from a single pair of simultaneous observa- 
tions, is 1,891 feet, or 39G foot less than that of the highest peak. 

It is within the walls of the Great Basin, and upon their summits, 
that the geology of Ktaadn can best be studied. The whole mountain, 
from the lowest point where rock in place has been discovered, is com- 
posed of granite. Of this, five specimens, numbered 3, 5, 23, 25, and 
57, have been examined by the lithologist of the Museum, Dr. Wads- 
worth, whose notes upon them ai-e here given. In a general description 
of the mountain, it may be said that it is made up of two varieties of 
granite, the gray and the red. To the first variety specimen 3 be- 
longs ; to the last, belong 23, 25, and 57; 5 being in a manner in- 
termediate between 3, on the one hand, and 23, 25, and 57, on the 

Dr. Wadsworth* s Notes. 

Kg. 3. 

— A gray granite, composed of feldspar, quartz, and biotite. The 
feldspar is of two kinda; a grayish-white one, with a piukiah tinge, is the most 
abundant, wliilc subordinate to it occurs a milk-white striated feldspar. The 
powder of the rock is magnetic. Under the microscope the thin section is seen 
to be composed of orthoclase and pkigioclasc, quartz, biotite, and magnetite. 
The orthoclase is much decomposed and cloudy, showing only feeble pohxriza- 
tiun. The plugioclase, in general, is much less altered, and shows its triclinic 
character well in polarized light. Some of the crystals, however, show the 
characteristic banding only in places, principally at the ends and sides of the 
crystals, while in the more altered portions the twiuucd structure is rarely seen. 
This alteration renders it very uncertain that the supposed orthoclase is really 
all so ; and we feel that this has been a fruitful source of error in the micro- 
Bcopic examination of rocks. The quartz contains numerous fluid inclusions, 
moving bubbles being seen in them ; it also contains trichites and minute 
crystals. These crystals are probably apatite and zircon. Some apatite crys- 
tals were seen in the feldspar. 



A pinkish gray granite of the same composition as No. 3, the dif- 
ference in color being due to the deeper color of the feldspar. It shows in the 

VOL. VII. — NO. 5. 14 



thin section similar characters to No. 3, except that the fehlspars are more de- 
composed, and therefore less plagiocLxse could be seen, while the quartz con-- 
tains more abundant trichitcs. 

No. 23, — A brownish red granite of similar composition with the preceding. 
Feldspars colored pink and greenish white. Calcite and a greenish talcose 
mineral occur as alteration products. In the thin section the feldspar is seen 
to be greatly altered, and but very little of it shows any trace of triclinic 
characters. The biotite is partly decomposed, and has a greenish color. The 
general character of the rock is slightly more basic than the two preceding, 
but we do not consider that there is enough difference to lead us to regard 
them as distinct. We should rather regard them as parts of the same forma- 

No. 25. — In this specimen the greenish feldspar predominates over the 

pink. The rock shows abundant signs of weathering, containing numerous 
cavities formed by the decomposition of its ferruginous minerals, and now 
partially filled with hydrous oxide of iron. Under the microscope this is seen 
to be the most decomposed of any of the specimens, the biotite being almost 
wholly changed, and almost no plagiockse being recognizable. Many parts of 
the rock are filled with viridite. The ([uartz, besides its numerous fluid inclu- 
sions, contains dodecahedral quartz crystals of the same character as those so 
commonly seen in the quartz of rhyolite. This rock is similar to No. 23. We 
should regard these rocks as eruptive, but we are well aware that others would 
claim that the microscopic characters are those which belong to metamorphosed 

sedimentary rocks. 

]S[o. 57. — This rock is seen in the hand specimen to be composed of fleyh- 
red orthoclase, pale greenish white feldspar, somewhat decomposed, together 
with altered biotite and quartz. Tlie biotite has been changed to a chloritic 
material. The minerals give to the rock a greenish red color. It is more 
coarsely crystalline than the other specimens from Mt. Ktaadn, and in its 
general facies is somewhat unlike specimens 3, 5, and 25. 

The lower two thirds of the baain walls are composed of the gray 
granite, which is similar in composition and appearance to that of the 
lower slopes of the mountain on the south side, and to that of Katep- 
skonegan Falls, except that the rock of the localities last indicated con- 
tains only the white feldspar. The upper third of the walls consists 
chiefly of the red variety (5), the modifications represented by Nos. 23, 
25, and ^7 being found only upon the vGry highest parts of the moun- 
tain, — the East and West peaks, the serrated crest, and the ridges that 
connect those portions. The rock represented by the last three num- 
bers is thrpughout so badly decomposed that only once was a specimen 
(57) obtained tolerably sound 'and firm under the hammer. The rock 
represented by No. 5 is oftenest, but not always, found in a crumbling 



condition; while the gray variety (3) is generally comparatively solid, 

but occurs in a few places in the last stages of disintegration. 

From the shores of the Basin Pond, where an unobstructed view is to 

be had of the whole height of the walls, the granite, up to two thirds the 

height of the eastern side, or about the upper limit of the gray varietv, 

is seen to be arranged in concentric sheets, that dip west at an angle 

varying from 45° to 60°. On the southern wall the same concentric 

arrangement prevails, the layers dipping north, often at angles higher 

than 60"^. Above the part that lies in concentric sheets is the red 

granite, which divides, on weathering, into blocks more or less regular 

in form. Near the head of a torrent that comes down from the Saddle, 

in two instances the red variety (5) lies in blocks, with forms so definite 

as strongly to resemble courses of cyclopean, but crumbling masonry. 

At the foot of these "castles" the rook is so friable as to fall into gravel 
under the tread. 

What has been said of the occurrence of the red and gray granites, at 
different elevations, does not mean that they are separated from each 
other by any well-defined horizontal plane. They arc undoubtedly parts 
of one and the same formation, and, as in the quarries of Quincy and 
Cape Ann a variety of rock having one color passes into a variety of 
another color so gradually that the separation cannot be said to take 
place along any line, or plane, so at Ktaadu the red and gray granites 
merge into each other in the same way, and at various levels. Yet it is 
substantially true that the lower two thirds of the basin walls, and 
probably the whole of the mountain mass below the level of the basin 
floor, consist of the gray, and the upper 700 feet of the red granite. 

As has been remarked already, the granite of Ktaadn is singularly 
free from dikes and veins. During the explorations made both in 1879 
and 1880, not a dike or vein was discovered, either .in the fixed or 
loose rocks of the mountain. We have seen that the same was true, 
with but two exceptions, of the ledges and bowlders that were observed 
upon the Penobscot. The absence of these characteristics of older rocks 
will be held to indicate that the granite of Ktaadn and its vicinity is of 
comparatively recent origin. 

The only considerable departure from the normal granitic type is the 
occurrence of very numerous inclusions which resemble imbedded frag- 
ments of foreign rock. Like patches are common in most granites, but 
I have never known elsewhere so many as the Ktaadn granite presents. 
Upon the talus beneath the east wall of the basin a small block of red 
granite was observed which contained five visible inclusions, varying from 



two and a half to seven inches in diameter. In respect to numborB, this 
was an exceptional case, bvit single inclusions met the eye at every 
turn. Of specimens collected in the basin, some have their outlines 
sharply defined, but others merge gradually into the enclosing granite. 
As usual, they are finer in grain, and of darker color, than the sur- 
rounding rock, being commonly of a deep gray, but sometimes ligliter 
from the presence of imbedded crystals of white feldspar. Upon the 
Southwest and East Slides a few inclusions were found of another char- 
acter. Of these, one was brought away from each locality, — the best 
of its kind. They seem to be fragments of almost black mica schist, 
arc angular on all sides, are separated from the granite by lines per- 
fectly distinct, and were selected as pieces of foreign rock which had been 
caught up by the granite and included within its mass. 

Inclusions in granite have long attracted attention, but have not 
been the subject of much investigation. A clear and extended discus- 
sion of their nature, with figures of specimens and a record of analyses, 
may be found in a paper, by J. Arthur Phillips, entitled '' On Concre- 
tionary Patches and Fragments of other Rocks contained in Granite." * 
In his '^General Conclusions," the author makes tlie following state- 
ment : ^'The inclusions contained in granite are of two distinct kinds. 
Those of the first class [which are spoken of throughout the article as 
concretionary, though not exiiibiting a concentric structvirc] are the re- 
sult of an abnormal arrangement of tlie minerals constituting the granite 
itself, while those belonging to the second represent fragments of other 
rocks enclosed within its mass." (p. 19.) Most of the patches observed 
in the basin must be assigned to the first class, while tl)e specimens 
brought from the slides seem clearly to belong to the second. 

The forms which the several parts of the mountain now present, and 
the condition of their surfaces, are largely due to the original structure 
and mode of weathering that characterize the rocks. As the highly in- 
clined concentric sheets in the basin walls break away, and fall upon 
the talus below, other faccy of equal inclination are exposed ; while the 
red granite of the higher parts, deprived of support, in turn gives way, 
and thus the steepness of the walls is maintained. Similar steep faces, 
due to the concentric structure of the granite, abound upon other parts 
of the moimtain, as on the flanks of several spurs, and about the base 
at various points. 

The crest (a feature unique among Eastern mountains) that occupies 
most of the space between East Peak and the Chimney owes its form and 

* Qaar. Jour. Gool. Soc of London, Vol. XXXVI. pp. 1-22, February, 1880. 

— -r -. 

- r ^^ -r 

■■ -^ '^■ni. "^r 



preservation to the circumstance that tlie modified red granite which 
malves it up divides in weathering into plates, which, when undistu,-bcd 
stand vertically on edge. They vary in thickness from an inch or less' 
to upwards of a foot. Where their trend is in the same direction as the 
ridge, there, as they have become loosened, and have fallen over the 
clilfs on either side, the plates still left firm in place constitute a nar- 
row crest. It is surmounted by a serrated edge, and, as one follows it 
for the fourth of a mile, alternately ascending steep projecting points 
and descending into jagged notches between, ho must again and again 
wallv along a mere blade of rock from one to two feet wide, having upon 
one side the yawning gulf of the basin, and on the other clilfs too" steep 
for climbing. 

From the crest southwest to East Peak, and between that and West 
Peak, the rock plates stand crosswise of the ridge at various angles, and 
there, as they have been loosened by frost, falling more or less out 
of perpendicular, they still remain. Thus the blade-like form is lost, 
and the ridge is somewhat wider, though still narrow. Bristling with 
oblique, projecting plates covered with black lichens, these parts pre- 
sent a savage and chaotic desolation that is probably without a parallel 
in Eastern North America. 

The very diverse conditions of surface upon the other summits 
hardly their forms — may be traced sometimes to variations in the 
jointing of the constituent rock, but oftener to simple difference in firm- 
ness. Thus, parts made up of the more friable red granite (other than 
those modifications of it, represented by specimens 23, 25, and 57 that 
divide into thin plates, and are confined to the highest siimmits only) 
are covered with small-sized fragments, rounded by decay. These at 
times assume, over wide spaces, the size, and almost tho arranc^ement 
of cobble paving-stones, and in a few places the aspect of gravelled 
areas. Such are soon chiefly on the northern summits. 

Again, the middle of the northward slope, between the Table Land 
and tlie Saddle, is piled with blocks of the firmer red granite riven 
from the mass beneath, of size so great as to render travel over them 
extremely difficult. The Table Land is in parts smoothed by a eoverin.^ 
of wholly disintegrated material, but in general is strewn witli tabular 
blocks that increase upwards toward West Peak in size and number 
The half-mile between the head of the great Southwest Slide and tlio 
brow above is literally a heap of huge blocks, constituting a slope that 
varies from 36° below to 47° above. 

The slopes south from the two chief pciiks are covered with loose 


m u Ai ^ _ ^iivvT ■ — ^1 \- vjt L ^ _ 




angular, often tabular fragments, as far down as to the tree line, 
wirich is every wlicrc upon the xnountaiu very low, leaving an unusual 
amount of naked rock above. These slopes present much the same 
appearance as does the top of Mt. AYasliington southward from the 
Summit House toward the Lake of the Clouds, except that on Ktaadn 
the blocks arc larger, and the slopes much more abrupt. 

All the summits so far described are bare of vegetable growth larger 
than lichens, or shrubs like the mountain cranberry, almost as diminu- 
tive as mosses, and are therefore open to close inspection. The whole 
rock surface has been so shattered that only on feces of cliffs too steep 
to allow the accumulation of detritus is rock in place to be found. To 
the east spur of Pamela, the " Horseback," the last statement will not 
apply. This narrow ridge may be said, in a great measure, to have 
shed its ruins as they have been formed. Consequently, the spur, over 
all its upper part, exhibits along the ridge abundant granite in place. 
Here, of course, the present surface is of recent origin. 

Except a few paragraphs in the brief accounts of hurried visits 
made to Ktaadn by Dr. Jackson and Prof. Hitchcock, contained in the 
Maine Geological lieports, a brief article by the late Dr. John De Laski,* 
of Vinalhavcn, and a reference of three lines in the second and third 
editions of Dana's Manual of Geology, based upon an erroneous state- 
ment of De Laski's, I recall nothing in print that specially relates to 
glaciation in connection with Ktaadn. Prof. Fernald's observations for 
the latitude of the highest peak make it to be 45° 53' 40'^ The par- 
all-el of 46", therefore, crosses the northern base of the mountain. Far- 
ther north than Mt. AVashington by over one degree and a half, and, 
according to the computation of Mr. W. H. Pickering, IGl miles distant 
from it in a straight lino, and of New England mountains inferior in 
altitude only to the highest summits of tlie Washington group, Ktaadn 
becomes of so much interest that, but for the inaccessible nature of the 
region, the mountain and its vicinity would long since have been thor- 
oughly explored for testimony upon the question of a great northern 
■ ice-sheet, and the existence of former local glaciers. 

As might be expected, upon summits changed from the original con- 
dition to the extent that has been indicated, days of search failed to 
discover any signs of glacial stride, or polish. Examination for them 
was made also, without result, on the lower slopes : first, where the 
trad from the Aboljacarmcgus Stream, about a mde from its beginning, 
crosses a succession of bare granite areas, and at the next exposure of 

* Am. Jour. Sci., [;3.] 111. IT- 27-31, 1S72. 









granite in the course of the trail, whicli is just at the foot of the pres- 
ent terminus of the Southwest Slide. At both localities the rock is of 
tiie coarse gray variety that is exposed at the third and fourth falls, 
and is destitute of glacial markings. The surffice is honeycombed by 
decay, which, at the lower station, lias gone so far that it was there 
impossible to break out, with a heavy hammer, specimens which at all 
approached a soiind condition. 

The only rock in place to be seen upon the Southwest Slide occurs 
two thirds the way up from its foot, at an elevation of about 3,500 
feet. It is a fine-grained, dark gray granite, approaching in appearance 
some of the inclusions that are found in the basin, and well adapted to 
resist decomposition. It lies, as at the stations below, in concentric 
sheets,* which have here an inclination of about 30°, a.nd is smooth, 
hard, and free from all indications of decay ; but not a scratch or 
other sign of glaciation appears upon it. It is a small area, only sev- 
enty-five feet along the slope, and perhaps a third as wide, and dis- 
appears above, below, and at the sides, under the debris of the slide, 
beyond the slanting face of which the ledge scarcely projects. If it w^as 
first uncovered, in recent times, hj the descent of the avalanche of 181G, 
as from the surroundings seems not improbable, the absence here of 
grooves and strite is significant as respects the glaciation of the higher 
parts of the mountain. 

If evidence of glaciation upon the sunmiits of Ktaadn exists, it must 
be other tlian that to be derived from smoothed and striated surfaces. 
It will bo maintained by many tliat such evidence is sup[)lied by the 
flat tops of the Table Land, and of several of the spurs, and by the well- 
rounded northern summits and faces. To this it may be objected that 
table~to])ped mountains are not wanting in regions where neither drift 
nor other indications of glaciation have been recoiJ:nized. 

The state- 


meut, however, \s open to the rejoinder that, in such cases, the shape 
may be rationally accounted for by obvious peculiarities of structure, as 
is the typical instance of Table Mountain, near the Cape of Good Hope, 
which is a mass of granite capped by horizontal beds of sandstone. 
The prevalence of steep faces upon the sides of Ktaadn, as already re- 

* My ob.servtitioii of Maine ^n-aiiitos in i,^ciu'Ta!, and ospceially at Mt. Ktaadn, 
foi'ccs inc to tlio conclusion that th(; conccnfric laniinalioii of ^n-aiiito is due to causes 
conitecicd witli tbc orii^dnal structure of the rock, and not, as has hoeu uiaintained 
by rrof(!ssors SJialcr and Jiunt, to superficial variations of toni})erature during tlio 
changes of the s(!iisoiis. It would seem, then, to be putting tonus in llu-ir hii^ncai 
oi'ih'r to speak of the coufornuly of preseul surfaces to the inclination of the "•riinitc 
sheets, ratlier than of the lanunation as confoi'inablc with superficial features. 

_^ ^LUUI- 






marked, is to bo ascribed ultimately to the high inclination of the con- 
centric sheets of granite; but there is absolutely nothing in the rock 
structure that will help to accounl for the existence of a great piano 
surface of above five hundred acres, like that of the Tabic Land. The 
supposition that it is the work of moving ice is a natural and rational 
one, provided the weight of proof in support of such an hypothesis is 
greater than that of proof antagonistic with it. But to cite testimony 
fur, or against, any particular theory, does not come within the scope of 
a brief piper like this, whoso chief purpose is the presentation of facts. 

Material interesting from its relation to the transportation of drift, 
whatever may have been the agent that moved it from the north, is 
not wanting upon Ktaadn. The two slides furnish the chief amount of 
such mateilal. The present Soutliwest Slide proper ~ the loose slide 
begins a little above the point where the old avalanclie started, a full 
half-mile below the brow of the Table Land, and terminates at the foot 
of the most abrupt portion of the mountain. The length between the 
points indicated, as estimated after repeated ascents and descents, is one 
mile and three fourths. The width at the bottom is ahout 100 feet, 
narrowing very slowly upwards. The difference of elevation between 
the top and bottom is 1,774 feet, — the mean of two observations. In 
its course the slide exhibits several terraces, at places doubtless where 
it conforms to the varying slope of the solid surface of rock over which 
it passes. The inclination, therefore, is variable. As tested with a 
clinometer at several points, it appears to be as follows. From the foot 
to the " Green Island," * a small bush-grown patch upon the surface of 
the slide, and ^S[) feet (mean of two observations) higher tlian its foot, 
the inclination of the slopes between tlic terraces varies upwards from 
24^ to 28° ; thence to the top it is 31°. The average inclination of the 
rock-pilod surface, from the head of the slide to the brow of the Tabl^e 
Land, is 35°, but the last seven minutes' climb is upon a slope of 47^ 
Along the lower two thirds of the slide, drift is distributed in consider- 
able quantity, but on the upper third it is rarely seen, and disappears 

entirely before the top is reached. 

Ilie East Slide is less than a mile long, and is one continuous slope, 
luiinterrupted by terraces like those of the Southwest Slide. The in- 
clination of the lower half was found to be 25° ; of the next fourtli, 28°; 
c»f the iq.per fourth, 30°. Its foot lies about 200 feet lower than tlio 
level of the I5asin Pond, and its head is 1,000 feet above the same level, 

-*■ A landinurk coasi.iciious for miles down llu;, and vecoginzablc i.i 



-.7»-jr.-Xr-.= =-= T^ r 



making the elevation of the head above the foot about 1,200 feet. It 
had its origin in an avalanche which is said to have descended between 
1820 and 1830. The two slides will in time disappear, as others before 
them doubtless have, by the slow encroachment of shrubby growth from 
the bottom and sides, now seen to be in progress. On the East Slide 
much less drift is found tlian on the other. Outside of the slides, I 
have never found drift upon the flanks of the mountain ; but it re- 
appears higher up, in very small amount on tlie Table Land, but princi- 
pally upon the northcru summits, sparsely strewn among the broken 
granite that covers them. Neither on slides nor summits is tiic drift 
ever found in large bowlders, but always as fragments of moderate size. 
On the Southwest Slide a few masses were seen as heavy as a hundred 
pounds each, but in general — always upon the East Slide — the pieces 
ran from a few ounces up to twenty pounds in weight. They were 
chiefly fragments of slates and sandstones, identical with the strata of 
the country north and w^est, mingled with pieces of metamorphic and 

trappean rocks, such as occur in place for a few miles beyond the llipo- 
genus Carry. 

The fragments of stratified rocks on tho Southwest Slide vcrv trcner- 
ally Include fossil shells, mainly Brachiopods, and always impressions or 
interior casts. Owing to the small size of the enclosing masses, — due 
to the fissile structure of the rocks, — the fossils ordinarily are much 
decayed, but occasional specimens are obtained in fine condition. .Amon<'" 
the scanty drift upon the upper third of the Southwest Slide, I have 
never seen a fossil-bearing stone. And upon those parts of tho summits 
where drift was found, only once w;is a fossil met with, — a solitary 
Brachiopod impression on a ten-pound piece of sandstone, picked up on 
tho slope northward from West Peak to the Saddle, about GOO feet be- 
low the top of the peak, or at an elevation of about 4,015 feet above the 
sea. This is by far the highest point at which fossiliferous rocks have 
yet been found upon Ktaadn.* 

* Dr. Dc Laaki's statenK-nt of tho height (4,385 foot) at which lie found fossils, 
"well up toward the * Horseback ' vidge" (Am. Jour. Sci., [3.] III. p. 27), and 
which is quoted by Prof. Dana in his Manual of Geology (e.litions 2d and 3(1), 
is founded upon a wrong estimate of the altitude of the mountain. He adopted 
the one current for some years before Prof. Fernald's remensuremcut of the eleva- 
tion, which he made to be 5,215 feet. Now the elevation of the "Horseback" 
ridge, at a point directly up from the head of the East Slide, — Dr. De Laski's 
route, ~ we make 1,181 feet above Basin Pond, while that of the summit of Ktaadu 
is 2,287 feet above the same level. The difference 2,287 — 1,181=1,100 feet, the 
difference of elevation between the "Horseback" ridge, at the point named, and 



For a purpose presently to appear, it is pertinent hero to introduce 
an observation made by Prof. Hitchcock in the valley of Avalanche 
Brook, a stream that, starting from the gorge between the Chimney 
and Pamola, abruptly terminates the East Slide by sweeping away the 
detritus at its foot, which the brook passes nearly at right angles. This 
" valley," where we saw it, is only a rocky channel, heaped with bowl- 
ders of all sizes. In the dry season there runs, half hidden among the 
rocks, a rivulet, which, in times of flood, becomes a furious torrent, and 
fills the banks. Says Hitchcock : '* We ascended the valley of Avalanche 
Brook on the south side of the mountain, and .... found an immense 
number of bowlders of Oriskany sandstone, many of them highly fossilif- 

crous We found none of these bowlders higher than the foot of the 

slide, although others have found them a few hundred feet liigher."* 

Among the other drift met with upon the slides, we found smoothed 
and striated stones, scratched uniformly in the direction of their length, 
and rounded at the angles. They are the first of their kind that have 
been reported from Ktaadn. The best were as fine examples of what 
are considered typical glaciated fragments as any that are figured as 
such in geological works. The largest, weighing from ten to fifteen 
pounds, were more deeply scored than the smaller; but being too heavy 
to be borne many miles in our packs, they were unwillingly left behind, 
and others of less weight were selected as specimens. Of two that wxre 
brought away, one is a piece of hard trap rock (determined by Dr. 
Wadsworth to be diabase) five inches long by two and a half at its 
widest part,. and weighing twenty ounces. The other is a thin piece of 
fine-grained argillaceous sandstone, seven inches by three and a fourth, 
split from some larger stone that was not discovered. Of such striated 
fragments not more than a dozen in all were found upon both slides. 
They were rare exceptions among drift that showed no stria;. Accord- 
ing to the testimony of books, and of several persons familiar with gla- 
cial phenomena from their own observation, the specimens agree precisely 
in character with stones worn at their angles, and grooved on their 
faces, under the ice of existing glaciers. It is of course impossible to 
conceive them to have been shaped and grooved simply by the friction 
they would have suffered in descending by gravity down the slide among 
the other debris. 

the summit ; and 5,215 ™ 1,106 =^ 4,109 feet, the hf^ight of the given point of the 
ridge above sea level. It was below tliis point, it will be observed, that Do Laski 
found his "upper fossils." 

* Prelim. Kep. Nat. Hist, and Geol. of Maine, p. 395. 

A-.V^- ^Vjlj^i^-v -^ 



All the facts in the case serve to hidicate that the non-granitic ma- 
terial found upon the mountain is a portion of the so-called "northern 
drift," with the fact of whose distribution- — not the manner — wo are 
here concerned. But we may and must suppose that in the distribu- 
tion the sides and summits of Ktaadn, as far up at least as 4,600 feet, 
received deposits of drift more or less in quantity. Through the action 
of gi'avitation the slopes have become loaded with fragments of granite 
that have been wedged from its mass by frost. Ktaadn has thus been 
buried under its own ruins, and beneath these ruins has been hidden 
the drift that was deposited when the mountain was comparatively 
intact. The avalanches which have produced the slides have brought 
to light along their course the covered drift. Near the starting-point 
of the descent, where the movement was superficial, little or none of 
the hidden material has been unearthed; but farther down, where the 
avalanche ploughed deep, more was brought to the surfiice. The shorter 
East Slide, therefore, which is superficial in comparison with the other, 
shows far less drift than does the Southwest Slide ; while Avalanche 
Brook, which flows over the steepest of the lower slopes, reveals in its 
deep channel more of drift than has elsewhere yet been found upon the 
whole mountain. There is reason to think that the bed of another 
stream, that runs on the north side of the East Spur, will, if followed 
up, yield like testimony. 

But while proofs of the former presence of an ice sheet upon Ktaadn 
are so scanty and questionable, seeming indications of local glaciation 
are not wanting. The location and surroundings of three little ponds, 
that lie just without the mouths of the basins, arc at least signifi- 
cant. Their waters are retained in place by low, irregular ridges, sit- 
uated just where terminal moraines of glaciers issuing from the basins 
would naturally occur. Those that hem in the second and third ponds, 
counting from the outlet of the chain, on the supposition that they are 


moraines, must have been deposited by glaciers that moved down from 
the North Basin. The ridges that hold the first pond, and separate it 

from the second, would seem to have been supplied by a glacier from 
the South Basin. Entirely satisfactory determination of the nature of 
these ridges is impossible while they are, as at present, completely masked 
by dense thickets ; but should fire hereafter lay them bare, opportu- 
nity will be afforded for thorough examination before a new growth 

springs up. 

The outlet of the first or lower pond is cut to the depth of about 

twelve feet, through a ridge of debris that appears to be the continua- 



tion of the one which runs along the eastern margin of the same pond ; 
and there can be but little doubt that the loose structure observed at 
the outlet prevails through the whole length of the retaining ridge. 
But as a running stream can speedily change stones over whicli it passes 
from irregular and angular forms to rounded and smoothed water-worn 
pebbles, such as now cover the surface at the outlet, no proof that the 
material of the ridge has the characters of a moraine deposit is attainable 
till an amount of digging is performed for which we had neither time 
nor tools. 

Half a mile from the point last named is a little bog, fifty by one 
hundred feet in extent, represented in the heliotype as a faintly drawn 
pond. Going outward from the basin, one steps from the surface of the 
bog directly upon the foot of a narrow ridge, which rises abruptly to the 
height of twenty feet, and as abruptly falls off on the opposite side to a 
level much lower than that of the bog. Its relations to the adjacent 
heights favor the view that it is the terminal moraine of a glacier that 
came down a wide depression of the mountain side, between Pamela, 
the " Horseback," and its flat-topped branch. The hollow is widest and 
steepest above, and would constitute a promising gathering ground for 
a glacier. So far as could be ascertained, without extensive digging, the 
elevation apparently consists of loose material, which might be regarded 

as moraine debris. 

Higher up in the same hollow, and nearly at the end of the flat- 
topped spar, is another diminutive pond, nestled behind what looks 
from a distance like the renmant of a moraine deposited later than 
the one below, and of which tiie greater part has been removed by de- 
nudation. These ponds will forcibly remind one who is acquainted 
with Viollct-lc-Duc's " Mont Blanc " of the small lakes held in place 
upon that mountain by like ridges, w^hich are described as undoubted old 


The mouth of North Basin is shut across by a low hill, to be seen 
in the heliotype. Viewed from the northern summits, it seems to be 
the last deposited terminal moraine of a glacier which once occupied 
that basin j but on closer inspection its aspect changes, and it is to bo 
regarded only as a possible, not a probable moraine. And, indeed, as is 
implied in the foregoing statements, the moraine-like form and location 
of the elevations which have been considered sliould be held, prior to 
thorough investigation, as indications that they may be, rather than 
proofs that they are, deposits from local glaciers. 

Whether the depression on the northern side of the *^^orseback" 




n-r. ■ i-r.-^ 



were more than ton feetr long. 

was, or was not, the track of veritable glaciers of a former period, it is now 
occupied at intervals by moving masses that approach as nearly to the 
character of glaciers as changed climatic conditions permit. The hollow 
is so broad, comparatively shallow, and smoothly concave in outline, 
that it cannot have been fashioned by running water, which on Ktaadn 
leaves its nuu'k always in deep and narrow gorges. At about the mid- 
dle of the concavity an open strip, ten or twelve rods wide, and com- 
pletely cleared of trees, runs down the slope, for more than a mile from 
the bare upper mountain, through thick woods below. The growth, at 
the intermediate point where we struck the strip, is one of spruces 
twenty feet high, that rise like a wall on either side of the square-cut 
opening; while the strip itself is covered with growing bushes that 
averaged, last September, less than five feet high. Among the buslies 
lay prostrate, with their tops pointing down hill, small spruce trunks, 
bleached and dry, and evidently for some years dead. None of them 

The dead trunks had been simply 
broken near the ground, and still lay attached to or near their bases. 
That the movement which cleared the strip is one that occurs only at 
intervals of some years, is proved by the considerable siza the trunks 
had attained before they were broken down ; and that at least one 
descent had taken place since that which felled them is shown by the 
fact tluit the eastern border of the strip, for a width of two rods, was 
free from bushes, but was covered with levelled spruces as large as those 
of the adjacent wood, and still retaining their branches and bark in 
nearly fresh condition. Here the thickness of tlie trunks was so great 
that they were not broken, but the roots were torn from the scanty 
soil on the upper side, leaving in the earth those that extended in 
the downhill direction. The mass that last descended was two rods 
wider on the east than any other which for many years had passed 
down the path. It must have levelled, for the time being, the bushes, 
wliosc elasticity saved them from breaking, and restored them to tlie 
upright position. 

The inclination of the hollow, through its wooded portion, is mod- 
erate for Ktaadn. It is evident that snow, accumulated on the bare 
and steeper slopes above, under conditions that have recurred only after 
periods of some years, has swept down as an avalanche with an impetus 
that bore it far over the forest-obstructed smaller slope below.* In 

* Under peculiar conditions, a trifling slope may serve, not only for the transmis- 
sion, bat for the origin of an avalanche. In Augusta a street, 100 feet wide, runs 
west from the river directly up the terraces before described to the ,g(^neral level 






its progress it has successively prostrated, buried, and passed over the 
opposing small trees, in no case, at the intermediate part which we saw, 
carrying away the trunks or branches. 

Certain huge blocks of granite that lie on the floor of the South 
Basin have been regarded by some as erratics, but m fact arc parts of 
the adjacent cliffs, and owe their present location indirectly to the 
agency of ice. They arc fragments of the eastern wall, which, falling 
upon inclined planes of compacted snow or ice accumulated in winter 
agahist the basin sides, have slid or rolled several rods beyond the 
great talus, 350 feet in height. Lying so far beyond the talus, which is 
the receptacle of most descending fragments, they have been mistaken 
for erratics, notwithstanding their agreement in composition with the 
nearest cliffs. In the same way alone can we account for the presence 
of great rock masses at stations so far out from the northern foot of Pa- 
mela that they cannot be supposed to have rolled thither over any other 
surface than an inclined plane of ice. Here, too, somewhat west from 
where the foot of the cleared strip must be, are four approximately par- 
allel ridges made up of granite blocks of all sizes. They are of consider- 
able length, and have between them hollows fifteen or twenty feet deep 
and some rods wide, but of unequal width. They appear too recent, — 
resembling parallel tali of fresh material, — and too near together, to 
correspond to my notion of old terminal moraines ; and I was unable 
to explain their origin in any way satisfactory to myself. 

A change that was produced in a part of the southern lobe of South 
Basin, dining the early summer of last year, is instructive, as illustrating 
the origin of the Ktaadn slides. The gorge between the Chimney and 
the peak of Pamela — a ty])ical instance of erosion — is a deep and nar- 
row cut, forty feet wide at its head, diminishing to ten at the foot, and 
upon its floor to two or three feet at the outlet, where it is a polished, con- 
cave water-course worn in the solid rock. Its small drainage area, and 
evidence derived from the accumulations about its foot, show that even 
in times of flood it ordinarily carries a stream of but moderate size. In 
■the summer of 1879 the debris that had been brought down in a series 
of years extended downward from the foot in the usual fan-shaped " cone 

ahovo. The hillside from the upper terraee to the top is 1,300 feet in length. The 
inelination of the street near the summit is 11" ; midway, 7^ ; below, IVom d" down 
to 0". Early in the winter of 1878-79, the snow, after continued rain, aysumed the 
slushy state, and, starting from the middle of the hill, whore tlie inclination is only 
7''y rushed suddenly down the street with a roar, and piled itself on the level ground 
at the foot. On the steeper upper half tlje snow lay unmoved. In the ninety years 
since the street was opened, tliis is the only ease of the kind recorded. 




of dejection," rendering passable the portion it overspread of the tahis, 
which, except at like phices, is ahnost inaccessible from its base, being 
there made up of hnge blocks like "monolithic houses tumbled together 
by an earthquake." The cone was furrowed by no deep cliaunel, such 
as would have been formed had a large and powerful stream passed over 
it. In September last the whole had been changed. Without pausing 
for details, it is enough to say that a gully had been cut to a depth of 
fifteen feet, down which, at a quarter of a mile's distance, was piled, 
twenty feet high, a heap of bowlders, varying from ten feet in diameter 
down to those of moderate size, all mingled with earth and gravel. 
Here the first rush of water which effected the change was checked, and 
its coarse deflected. Lower down, smaller blocks were distributed in the 
order of their size ; then came cobbles, next pebbles, then gravel, till at the 
distance of more than half a mile, and near the Basin Pond, one stepped 
suddenly down from a square-ending sand terrace two and a half feet 
high. Such an exhibition of material assorted by watei-, within so small 
a space, is rarely to be seen. A watcr-spout, or "cloud-burst," upon the 
peaks had wrought the havoc. It must have been confined to a nar- 
row area, for signs of disturbance were wholly wanting on the talus lialf 
a mile north; and in the bed of the torrent, less than a mile distant, 
which descends from the Saddle and was both years our daily route from 
camp at the Basin Pond to the summits, no change from the previous 
year had happened. The time of th<3 occurrence was fixed by valid 
proof. Scrnb birches were found in the course of the flood completely 
stripped of bark, but often retaining at the tips ot their highest twigs 
shrivelled leaves, which showed by their thinness that the shrubs had 
been torn from place just as the leaves were fully expanded. 


Heliotype taken from a model of Mt. Ktaacln, representing the upper three 
thousand feet of the mountain, and an area of about ten miles in length hy seven 
in width. The vertical scale of the model is three times greater than the hori- 
zontal. Lack of shade renders some of the features indistinct. 






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Paper- on the 

Geology OF Mr. Ktaadn. 

j.w.<&j. Sc.waii,a.h:'s. 







^^''i^-KefuKyp^Pnnlin^ i.bji/ 7>^f»ofiicVJfosfo?i. 


No. 6. — Report on the Recent Additions of Fossil Plants. By 

Leo Lesquekeux. 

In the department of Paleophjthology the collections of the Museum 
have been this year greatly increased by the following contributions : — 

1. The Smithsonian Institution has presented one hundred specimens 
of tertiary and cretaceous plants, obtained by the U. S. Geological Sur- 
veys of the Territories imder the direction of Dr. F. V. Hayden. They 
are referable to species published hi the Cretaceous and Tertiary Floras, 
Vols. VL and Nil. of the U. S. Eeports. 

2. More than six hundred specimens of cretaceous fossil plants have 
been obtained in the Dakota group of Kansas by Mr. Charles H. Stern- 
berg. These specimens, in a remarkably _ good state of preservation, 
represent forty specific forms, of which about twenty are new, and six 
known only as yet by the descriptions of Professor Fleer. 

The new species arc referable, like those published already from this 
formation, to all the essential divisions of the vegetable kingdom. ^ The 
Cryptogamous have fragments of a Jeanpmdia ? and of an Equisetum, 
The Conifers are represented by a large TImites ; the Cycadese, by three 
or four species, of Podozarmtes. The Phomogamous Apetaletv have a 
Mi/rica, an Al/iiteSj a Qucrcus, two species of /Vcms, and ti Laui^opkyllum ; 
the Dialypetale(E^ an Aralia, three distinct forms of A raliopsisj a Cissus, 
four species of Liriodendron, an Anoua, a Greviopsis, a Sapiudus, and a 
Ehamnas. Besides these new species there are in the collection ^>Qii\- 
mQusol Popuhts litil</iosaj Ficus primordialisj Dios2}yros primo'va^ already 
described by Ileer from the Dakota group, with Protcoidcs lancifolius^ 
described by the same author from the European Cretaceous of Qued- 
linburg, and Magnolia speciosa, from that of Moletin. Some other very 
rare species, like Popidiies elegans, Platanus primmva^ Magnolia tenuifo- 
lia, Liriodendron giganteum, Aralia Towneri, Aralia sapoi^tanea^ divers 
species of Protophyllum, and especially Aspidiophylhim trilohativm, are 
represented also by numerous beautifull}'" preserved specimens. Taken 
all together, this collection is therefore a valuable acquisition for the 


VOL. VII. — NO. 6. 





It is not less valuable in regard to the data which it affords in con- 
firmation or contradiction of Komc of the general conclusions derived 
from the examination of the materials formerly described from this 


peculiar cretaceous flora. 

For example, the disconnection of the flora of the Dakota group from 
that of the older ones, those of the Jurassic times, does not appear now 
as positive as formerly, or as it was indicated in tiie Cretaceous Flora, 
Vol. VI. of the U. S. lleports. For besides the Pterophylkim described 
in that volume as somewhat doubtfully refei^able to the Cycadcix;, plants 
which essentially constitute the vegetation of the Jurassic, we have now 
four species of the genus Podozamites either identical with or closely 
related to species known from this formation. 

Per contra^ the disconnection of the Cretaceous flora from that of the 
lower Tertiary appears now still more evident, as the new species do 
not indicate any afiinity to the plants of the Laramie group, which is 
positively Eocene by its types. As yet no vegetable remains distinctly 
referable to Palms have been found in the Dakota group. 

The vegetation of the Cretaceous seems to be essentially composed of 
synthetic types, genera or groups of plants of analogous characters, 
which it is extremely difiicult to define and separate into species. And 
nevertheless, when considered separately, the leaves, which are as yet the 
only organs obtained for analysis, show points of diftcrence so marked 
that it is not well possible to consider them as representing mere varieties. 
To prove this assertion, it is sufiicient to examine the so-called species 
described imdcr the generic names of PopuUtes, Platamis, Araliopds (a 
new division which includes most of the leaves described as Sassafras), 
Aralia, Protcqihylluin, Menisperiniies, etc. One of tliese types, however, 
the more peculiar and distinctly cretaceous in its facies, Liriodendron, 
was until now represented by few diversified forms, and therefore con- 
sidered as simple, and the supposition seemed confirmed by its passage, 
with Platama, Sassafras, and Far/us, through all the geological ages from 
the Cretaceous to our time, with scarcely any modifications and few 
representatives. But now (he collection of Mr. Sternberg eliminates 
this exception, as we find in it four new and very distinct forms of tliis 
rronp, besides a beautiful entirely preserved leaf of Liriodendron (jiyan^ 
teum, which had been described from a mere lateral lobe, and which w^as 
therefore of uncertain attribution. 

A short descripti(m of this genus, and of its species as ex])oscd by the 
leaves, may show how uncertain, though binding, are the characters of 
the Cretaceous leaves. 




Genus Liriodendron, Leaves panduriform, oppositely biloLed ; lobes oblique 
or in right angle, obtuse or acuminate ; midrib thick ; lateral veins in ri^rht 
angle, opposite or irregularly alternate. ^ 

1. L. gigcmteum. Leaves large, twenty centimeters broad between the lower 
broad (six centimeters), oblong, obtuse or rounded lobes ; upper lobes shorter, 
slightly turned upwards, narrowed and rounded to an obtuse point, joining the' 
lower in an obtuse sinus at a short distance (two centimeters) from the mtdial 

This form is the one more distinctly related to Liriodendron tulipifera, 
the species living at our epoch. It cannot be considered identical with 
it, however, the difference in the characters of the leaves being too 
marked, but not more so than in the following forms, which I consider 
as new species. 

2. Liriodendron acuminatum, sp. nov. Leaves small, about half as large as 
in the preceding species, cut in two pairs of narrow linear acuminate lobes, 
about one centimeter broad, all curved upwards. 

3. Liriodendron cntciforme, sp. nov. Leaves large, upper lobes broad, square 
or equilateral, in right angle to the broad midrib ; lower lobes narrow, linear, 
acuminate, much longer and turned upwards. The shape of the leaves is like 
that of an anchor, except that the medial nerve or axis does not pass above the 
upper borders of the lobes. 

4. Liriodendron semd-alatum., sp. nov. Leaves divided at the base in two 
opposite short rounded lobes (one on each side) curving up to near the medial 
nerve and then enlarging upwards into an obovate or spathulate entire lamina. 

6. Liriodendron pinnatifidum, sp. nov. A single leaf with the general facies, 
and the' venation of a Liriodendron, but subalternately trilobate on each side.' 
The top of the leaf is broken. 

Besides the above forms, there have been described already, from .the 
Dakota group, Liriodendron Meekii, Heer, a species with comparatively 
small leaves, only three to five centimeters long, two to four centimeters 
broad, the lobes equal in length, short and rounded ; and Liriodendron 
primavum, Newb., from a leaf of which the upper half is destroyed, and 
Whose characters are not sufficiently defined. By the size of the leaves, the 
species is intermediate between L. Meekii, Heer, and L. intermedium, Lsqx. I 
form also known from a single lacerated leaf, which, narrow in the middle' 
has long obtuse lobes turned upwards, and a facies different from that of 
any of the other forms described. We have thus eight specific forms of 
leaves representing the clearly defined type or genus Liriodendron, all dif- 
fering so greatly that it is not possible to consider them as mere varieties 
of one species only, and nevertheless of characters so closely allied that 
their specific identification seems to be hazardous. And this, as said 
above, is the case with most of the so-called species of the Dakota group. 




The difficulty is increased by the fact that by gradual modification the 
leaves pass to evidently different generic types. The genus Liriophyl- 
lum, for example, represents leaves of Liriodendron nearly round in out- 
line, but split at the top and to below the middle in two lobes joined in 
a narrow sinus upon the medial nerve, a peculiar division and facies 
which have no analogy in any species of plants of our epoch. This new 
genus is by its leaves intermediate between Liriodendron and Fopulus. 

The local distribution of the leaves may be relied upon to give some 
directions for the separation of species. For of course if the analogous 
forms are found in separate and distant localities, the marked differences 
are more likely to be specific. On this subject the specimens collected 
by Mr. Sternberg afford good opportunity for examining the question. 
Omitting details, it suffices to mention what is known of the distribution 
of the leaves of Liriodendron. 

L, Meekii is described from specimens found in Nebraska and Minne- 

sota only. 

The specimen of L. primavran is labelled Blackbird Hills, 
This form is allied only to L. semi-alatum of Kansas. L. in- 

termedium is also from Nebraska, represented in one specimen only, and 

has no affinity with any of the Kansas species. L. giganteum was first 

described from a fragment found near Fort llarker, Kansas, while the 

specimen of the Museum is from two aud a half miles from Glascoe, in 

another county, where also were found L. acuminatum and Z. pinna- 

tifidum, whose leaves have little affinity of characters between them. 

L. semi-alatum was found at a different locality seven miles distant from 

Glascoe, and Z. cruci/orme at Elkhorn Creek, twelve miles northwest of 


From this kind of distribution it seems legitimate to conclude, not 


only for Liriodendron^ but also for all the other groups of this flora 
whose leaves present the same degree of affinity or of difference, that, if 
the forms are derived from synthetic types, and if they are found some- 
what modified in characters at distant localities, it is a proof that the 
modifications are already fixed, have become local characters, and that 
they may be considered as specific. 

On another question, that of the derivation of the vegetable remains 


found in the strata of the Dakota group, and of their distribution, either 
in place, from trees grov/n there, or as transported by water from dis- 


taut localities, a question examined already in the Cretaceous Flora, the 
collection of Mr. Sternberg affords the same degree of evidence as for 
the preceding. 

It has been observed in the Flora, Vol. VI., loc. cit, that the Creta- 



ceous leaves and other remains of plants are found always spread over 
small areas, generally less than one or two acres in surface, and far dis- 
tant from each other, so that in travelling over the prairies of Nebraska 
and Kansas, the collector may wander for twenty to forty miles or more 
without discovering a single fragment of fossil vegetable, and abruptly 
come to one rich deposit where leaves are found in abundance. Gen- 
erally each of these deposits has remains of plants of a peculiar group, 
even sometimes of a single species. For example, Aspidiophylliun. leaves 
are from one place only ; Aralia Saportanea, from two widely distant. 
Protophyllivm and Sassafras^ or Aralwpsis cretaceus, and its varieties 
abound at Thompson's Creek, while species of Salix and Podozamites 
are from Elkhorn Creek and Glascoe ; and so on. The localities where 
the specimens examined were found are twenty in number, and iri each 
of them only two to a dozen species have been recognized. A group- 
ing of this kind shows that the leaves were derived from trees grown in 
place where the leaves are now found, the trees apparently covering hil- 
locks, or dry surfaces of land, disseminated in wide lagoons. As floated 
from a distant shore, the leaves should be more or less, but always, 
mixed. Their fine state of preservation, their position generally flat, 
confirm this supposition. 

3. A second lot of specimens from the same formation has been pro- 
cured for the Museum in Colorado, near Morison, by Ile^", Arthur Lakes. 
The number of specimens is small, and the species which they represent 
are all, except one, already known from the Dakota group of Kansas. 
Among them are Proteoides grevilliceformis, P. dapknogenmdes, Magnolia 
alternaris, M. Capellini, described by Heer in the Phillites of Nebraska, 
Sassafras cretaceus, Newb., Salix protecpfoUa, with Liriophylliim populi- 
folmm, L. Beckio'dhi, Aralia Toionerl, Stercidia lugubrts, and species of 
Ficiis, most of them found in Kansas, and already figured for the eighth 
volume of the IJ. S. Reports. One of the species only, a peculiar small 
form of Liriophylkmiy is new. 

4. The last addition of this year to the phytopakrontological depart- 
ment of the Museum has been made by the acquisition of nine hundred 
specimens of coal plants from Mr. T. T. Mansfield of Cannelton, Pennsyl- 
vania. This locality has until now furnished to the coal flora an abun- 
dance of vegetable remains of species rarely found elsewhere. Of the 
genus Gordaites, for example, formerly known by separate leaves or 
mere fragments of leaves only, specimens have been found there with 
branches bearing leaves, and even flowers and fruit. A proportionately ■ 
largo number of specimens of this kind are in the Cannelton collection, 

« « 


which represents fifty species, mostly in finely preserved materials. 
Among the species worth mentioning are Odontopteris cornuta, Callipte^ 
ridium inrequale, Akthopteru ambif/ua, divers species of Stemmatopteris 
and Caulopterls, Lepidostrohus sp)€ctahilis, Lepidophyllum Mansfieldi, Spo~ 
rocystis and Lepidocystis species, Tmiiophyllttm decurrens, Khahdocarptis 
Mansfieldi, all peculiar to the locality, or not as yet found elsewhere, 
and splendid and numerous specimens of the rare spikes of Macrostachia 
infundibuliforinis, Nearopteris cordata? Brgt., or Cydopteris-trichoma- 
noides ^, N. heierophylla, Brgt., Pseudopjecopteris PlucJcneti, and P. anceps ; 
many specimens of Spiropteris, circinnate branches of ferns (spirally 
coiled inward in the process of unfolding), of Sigillaria monostigma, of 
Artida (decorticated stems of Cordaites), of Cordaianthus (their flowers), 
of Gordaicarpus (their fruits), etc. As the Museum had not any spe- 
cimens of that peculiar locality, these plants constitute an important 

addition to the collection. 

With the materials obtained this year the Museum has now in fossil 

plants : — 

1. From the Devonian, a series of specimens presented by Professor 

J. W. Dawson and Mr. C. T. Hartt from the measures of Canada, and 

rom England a number of very fine ones, presented by Sir Charles 

Lyell. Among these is a splendid fruiting pinna of Arckceopteris Hyher- 



2. From the Carboniferous, a large number of the best specimens 
found in the nodules of Mazon Creek, the shales of Morris, and other 
localities of Illinois ; numerous and good specimens from the anthracite 
basins of Rhode Island and of Pennsylvania ; fine materials from divers 
localities of Ohio and Kentucky, presented by Mr. Anthony ; rare speci- 
mens from the subconglomcrate measures of Ohio and Tennessee ; and 
the collection of Cannelton mentioned above. 

3. From the Cretaceous of the West the Museum has now an amount 
of materials sufficiently representing the Dakota group. Fine and nu- 
merous specimens can be spared for exchange. 

4. The Tertiary of this continent is insufficiently represented in the 
Museum by a number of specimens presented by the Smithsonian Insti- 
tution, and by a few sent by Kev. Arthur Lakes from Golden, Colorado. 
There is, per contra, from Europe a splendid collection of Miocene 
plants purchased from Professor Heer, of Zurich, and a number of un- 
determined specimens from divers formations and localities, mixed with 
animal remains, in the collection of Bronn. 


]N"o. 7. — The Great Dike at Hough's JVecIc, Quincy, Mass. By John 

Eliot Wolkk 

Tins dike is situated some two and a lialf miles northeast from 
Qiiincy Depot ; rising, when first seen, as an irregular ridge, and con- 
tinuing, with interruptions, for ahout a mile in an easterly direction. 

Mr. Crosby has mentioned this locality in his "Contributions to the 
Geology of Eastern Massachusetts ":* — ''On Hough's Neck, in Quincy, 
the amygdaloid is a green, slaty rock ; it is sometimes ifmygdaloidal, 
and sometimes porphyritic, and includes masses whicli resemble fclsitc. 
It occupies the axis of an anticlinal in the conglomerate ; and also cuts 
the latter rock very freely, after the manner of an eruptive." (p. 17G.) 
Again :^ "On Hough's Neck, in Quincy, along the north side of Hock 
Island Cove, there are prominent ledges of conglomerate flanl^ing a large 
mass of amygdaloid, and the latter rock crops through the former in iso- 


latcd bands, due to extravasation or faulting. The conglomerate strikes 
about east-west, and shows nearly vertical dips to the north and south, 
dipping away from the amygdaloid. It holds unmistakable pebbles of 
Shawmut breccia. This is clearly a faulted anticlinaj fold. Toward 
the north, over the area marked as slate, the rocks arc all concealed by 
drift ; but on the south the conglomerate shows very plain indications 
of a passage to slate." (p. 200.) The amygdaloid, constituting a mem- 
ber of Crosby's Shawmut group, is regarded by him as older than the 
overlying Primordial conglomerate, and as a sedimentary I'ock in general, 
though sometimes presenting evidence of intrusion. 

The country rock of the dike is a coarse conglomerate, with occasional 
interbedded layers of red sandstone and slate. At the eastern end it is 
bordered on both sides by the conglomerate. After running for a quar- 
ter of a mile as a ridge, the dike suddenly loses its ridge character, and 
occasional exposures only are found in the field to the cast, among the 
outcropping conglomerate ledges. It can bo traced thus for a quarter 
of a mile ; then for some hundred feet no outcrop of dike is found until 
a small creeli: is reached. Crossing this, however, we again find a 
dike continuing as a ridge in the same direction for some hundred yards, 
when it disappears under the drift of a headland. This exposure, how- 

* Occas. Tapers, Bost. Soc. ]N[at.IIist., III., 1880. 


VOL. VJl. 

xo. 7. 




ever, is not in the line of strike of tlic. main, or westerly part of the dike, 
but lies some hundred feet to thj north. Whether this ehange is due to 
a horizontal throw^ or to a fresh outbreak of dike along a parallel line, 
does not appear. 

At the western end, on the southern side, the jnnetion with the con- 
glomerate and red sandstone is very irregular, — large and small tongues 
of the dike penetrate into the conglomerate, this rock having a strike 
N. 60°-80° W., and a dip 70° south. The jmiction between the two 
rocks is sharp and well marked : the dike seems often amygdaloidal near 
the junction. Sections of the contact of the two rocks show that the dike 
is composed of a mass of very small feldspars, having a beautiful fkiidal 
arrangement, while they are often bent when in contact with the line of 
the conglomerate. On the northern side, a fine vertical exposure of the 
junction is obtained, which is seen to stand almost vertical ■ the dike 
cutting the slate and conglomerate a little irrcgularl}^, but standing 
nearly parallel to the stratification. The conglomerate hero is nearly 
vertical, but may be said to dip to the north very steeply; if, however, 
v/e pass east along the strike, a few hundred yards, to the exposures in 
the field, we find that all the conglomerate, both north and south of the 
line of the dike, dips steeply in one direction, i. e. south. I cannot, 
therefore, agree with Mr. Crosby, that " this is clearly a faulted anticlinal 
fold." It may equally well be an intrusion of the dilic into the verti- 
cally standing strata, causing irregularities of the dip. More detailed 
study is required. In the western ridge the dike has a width of about 
three hundred feet from contact to contact. 

The rock is generally of a greenish color, approaching a greenish red 
in the fresher portions ; it is irregularly jointed. In texture there is 
great variation between coarse, fine, porphyritic, and amygdaloidal. 
Masses of quartz, and yellowish-green epidotic material frequently occur. 
These greenish masses are often very irregular, occasionally vertically 
banded, and resembling fragments of a stratified rock, and often lined on 
the exterior with a band of reddish substance. Microscopic sections of 
some of them give a mixture of quartz, calcite, cpidote, and a whitish 
opaque substance (kaolin 1), and show that they are in part areas in the 
rock of decomposition, or segregation. 

Although at first sight this dike appears to be a homogeneous mass of 
rock, yet it is in reality composed of rocks belonging (in all probability) 
to at least three separate eruptions, forming, instead of one, numerous 
dikes. To this fact is largely due the noticeable variations in the area 
of rock. First in order comes the amygdaloid, forming the principal 










mass of the rock, and eruptive through the conglomerate. In the 
second place, a close study of the great area of this rock shows that 
it is cut by a large number of naiTow diabase dikes, generally but a 
few feet in width (e. g. three feet), which do not have a marked amyg- 
daloidal structure. In many cases they run almost parallel with the 
trend of the amygdaloid ; in other cases they run obliquely, while 
others again may cut almost transversely across it, in parallelism with 
a third dike to be mentioned. These dikes show generally welhmarkcd 
contacts with the amygdaloid : they are fine-grained_ at the junction, 
but coarse-grained in the centre ; in some cases they have melted 
the amygdaloid at the contact, so that it is difficult to find the actual 
line. Some of them are easily distinguished from the amygdaloid, un- 
der the microscope, by the large amount of augite which they contain, 
but in others this mineral cannot be found as such, for all trace of it 
(if originally present) has been lost in the alteration products. Lastly, 
about the middle of the large western exposure of the amygdaloid there 
is found a large dike (at least seventy feet wide) running transversely 
across it, in a direction N. S^'-IO" W. On the south side it is seen 
breaking through the conglomerate and sandstone, and can be traced 
from that locality across the amygdaloid. No exposure was found giving 
the actual contact of this rock with any of the others, although it can 
be seen at a distance of a foot or two from them. Judging from its 
direction, which cuts directly across the trend of a great number of the 
small dikes, it would seem to be the latest rock of alL Some of the 
small dikes to the east of it are, however, nearly parallel with it. While, 
therefore, there seem to be at least two periods of eruption subsequent 
to that of the amygdaloid, yet some of these small dikes may cut the 
others, thus complicating the phenomena still further. I have not been 
able to find evidence of this beyond the difference of direction; and to 
settle the question by the discovery of the actual contacts will be diffi- 
cult, on account of the lithological similarity of all the eruptive rocks, 
and the thick covering of lichens, which conceals everything, and makes 
any work there laborious. 

The amygdaloid sometimes loses its amygdaloidal character, so as 
to resemble greatly the later dikes ; but in such cases the passage is 

The microscopic descriptions which follow show that all these rocks 
are altered basalts, and, together with the field relations, prove that 
they are all truly eruptive rocks, breaking through tbe conglomeratej 
while the later eruptive rocks cut the earlier ones. 




[l.J From Western End of Dike ^ North Side, near the Road, 

small Dikes in the Amygdaloid. 

one of the 

Lens.^ A greenish-gray, fclty-looking rock, containing minnte grains 
of pjrite, and small feldspar crystals. Traversed by vcinlcts of epidotc. 
— /Section, White opaque feldspar crystals, and masses of opacite, niug- 
nctlte, and pyrite, in a green chloritic groundmass. The feldspars have 
generally the long ledge form of the basaltic triclinic feldspars, but 
occasionally the form of Carlsbad twins of sanidin. They are entirely 
altered to a fibrous and sc^i,ly aggregate, polarizing with yellow and blue 
colors, — often with the brilliancy of talc. Colorless needles with cross 
fracture (apatite) occur occasionally in the feldspars, and also aggregate 
quartz. Between the feldspars lies a mass of green fibrous products, — ■ 

chlorite, viridito, etc., considerable epidotc, magnetite, quartz, etc., 
rarely hematite and biotite. The magnetite often has the form of a 
grating, reminding us of decomposed olivine. The feldspars occasion- 
ally have a :f!uidal arrangement. 

[2.] Contact of Amygdaloi/l and GongUnnerate at Southeast Corner. 

Section. A mass of small feldspar crystals, having a well-marked 
fluidal arrangement, and surrounding decomposed crystals of olivine and 
masses of magnetite and opacite. The olivine crystals have the charac- 
teristic lozenge shape, blackened border, and irregular fissuring, while 
the small parallel feldspars of the groundmass separate and How around 
the crystals. Some are altered within the black border to a light green 
serpentine with fibrous polarization ; in others, wliile the centre shows 
the brilliant polarization and the pitted surface of olivine (though the 
greenish color is evidence of some alteration), the exterior zone of the 
crystal has been altered to a bluish-gray substance, vdiich in polai'ized 
light is seen to contain fibres with brilliant polarization, and msiy per- 
haps represent a stage in the alteration to talc. Some of the olivines 
are wholly or partially altered to ferrite and talc, the latter polarizing 
very brilliantly. Some of the magnetite and opacite in the section is 
derived apparently from the complete alteration of grains of olivine. 
The feldspars have generally the long ledge character of the l)asaltic 
feldspars, though some have the form and optical properties of Carlsbad 
twins. Occasionally there is found a crystal sufiiciently fresh to show 
the multiple twinning, but generally they are filled with greenish or 
transparent scales, while along the centre of the ledge crystal there 
runs a line of green chloritic material, containing generally less opacite 

k I 



than the similar substances lying outside the crystal, but often continu- 
ous with them. Some of the crystals arc more than half filled in the 
centre by a I'ectangular mass of this chlorite, often extending through 
to connect with that outside. The space between the feldspars is occu- 
pied by chloritic materials, opacite, etc., together witli some quartz. 
Epidote and quartz occur in the groundmass as alteration products, and 
transparent needles, frequently broken across, which are probably in part 
apatite. Along the line of the conglomerate some of the feldspars are 

[3.] West End of Amygdaloid vevf/ near [1] 

Lens. A gray-colored groundmass, containing white and greenish 
feldspar crystals, spots and crystals of epidote, occasional quartz and 
epidote amygdulcs, and reddish areas of decomposition. — Section. Com- 
posed princi])ally of feldspars, with considerable epidote, chlorite, opacite, 
etc. The feldsjxirs are mainly plagioclase, but there are occasional 
Carlsbad twins of sanidin. Some of the large porphyritic feldspars 
arc broken and fragmentary; an effect, apparently, of the ilowing base, 
for the small feldspars diverge, and flow around the large crystals. In 
some cases tliey are seen to have been pnslied into the large crystals 
a certain distance on opposite ends along the central line, while a line 
of base passed through tlie crystal connecting the two tongues. Tliis 
base, however, is now altered to calcite, chlorite, epidote, etc. Occasion- 
ally two feldspars interpenetrate each other. The products of their de- 
composition are the same greenish or colorless scales (which often have a 
brilliant polarization), epidote, chlorite, calcite, quartz, and colorless nee- 
dles. The smaller feldspars seem less decomposed than the larger ones. 
Between the feldspars lie masses of chlorite, epidote, opacite, calcite, 
magnetite, etc. ; often in the form of wedges between the divero-i 

One grain of altered olivine is seen in the section, identified l)y 
the shape and the previously described motion of tiie aroundmass and 
base around it. The exterior consists of reddish ferrite, penetrating 
along the fissures ; the interior of quartz. ^ 


-,mg fold- 

[4.] West End of the Avujgdaloid near [1] and [3], hut nearer in the Cen^ 

tre of the Mass. 

Lens. Similar to [_:^-]. ^ Section. The large feldspars are broken by 
the base, as descri])ed above. Plagioclase and sanidin occur. True 
amygdules occur here, recognized as such J)y the regular shape, and by 
the fact that the small felds])ars of the groundmass flow around the 



ca,vity and are distinctly separated fi'om it. They uj-c filled with cpi- 
dote, chlorite, calcite, quartz, and a fii)rous chalcedonic (?) material : 
the epidote is generally on the outside, tlic chlorite inside. Consider- 
able epidotc is seattered througli the section, generally outside of the 
feldspars, and also talc, caloito, and quartz. 'J'heso dcconiposiLion ]}rod- 
nets often occnr in th.e groundmass in rounded areas, but are not true 
amygdaloids. Patches of reddish opaqne ferrite also occur in a similar 
manner, constituting the red spots seen macroscopically. 

[5.] Western Ridije of the Dike cm the West Side of a Road which crosses 

it, — taken towards the Cadre of Uie Mass. 

Lens. A greenish groundmass containing porphyriiio feldspars, red- 
dish and greenish areas of alteration, and rounded masses of (piartz. 
The groundmass has intruded into some of the large feldspars. 
Section. Crystals of feldspar and areas of decomposition or iufiltration 
surrounded by a greenish chloritic mass. The Luge ieldsi)ars ar(! occa- 
sionally Carlsbad twins; the small ones of the groundmass piincipally 
plagioclase, although some are twinned sanidin crystals. The (original) 
base, carrying small feldspars, has bent some of the laigo feldspars, and 
pushed into them. Others contain in the centre square zonsd inclusions 
of the greenish mass, while the outer zone of the crystal is free frum 
it. These phenomena are similar to those so frequently observed in the 
unaltered basalts with a glassy base. Many of the hirger feldspar cr)'sLals 
are partly filled with epidote grains,, chloritic material, and light^green 
needles, which have a yellowish-white polarization. Ptouuded areas, com- 
posed of greenish chloritic fibres, with sometimes a deep violet blue 
color between Crossed nicols, occur in the groundmass, niiu<dcd occa- 
sionally with talc, and bordered by epidote. Some of these ai'cas, en- 
closing the remains of the small feldspars, arise fi-om the decomposition 
of the groundmass ; others are either true amygdules, as described above, 
or some might be pseudomorphs after some mineral, — for instance, oli- 
vine. Between the feldspars lies tlie gi'een mixture of chlorite, viridite, 
and greenish needles f^imilar to those described in the feldspars, beside 
some epidote, calcite, and quartz. 

[G.] Western Ridije of the Amygdaloid, ahout fifty feet east of a Road 
crossing it, ~ the Specimen taken from, a long Dike crossing the 
Amygdaloid obUqnely to its 'Main Trevd. 

A grayisli-grcen groundmass, holding crystals of greenish 
feldspar and grains of ])yrite. The groundmass has pushed into some of 















the long crystals. Powder feebly magnetic. — Section. Mnch decom- 
posed. The feldspars retain their outline, but are liiled with chloritic 
niaiei-ialj — kaolin, epidote, and calcite. Magnetite is very plentiful in 
crystalline and irregular forms, having often a whitish, decomposed sur- 
face (leucoxcno), wliich, in connection with the reticular or branching 
shape of the masses, shows the presence of mcnaccanite. Pyrite occurs 
in occasional grains and square crystals, generally close to or mingled 
with the magnetite or decomposed menaccanite, and is therefore proba- 
bly an alteration product. The remaining portion of the rock is a con- 
fused mixture of chlorite, cpidote, quartz, viridite, hornblende, calcite, 
and colorless needles, in part probably apatite, — all products of altera- 
tion. This rock is the most coarsely crystalline and the most decom- 
posed of any examined. 

[7.] From the Exposicre of the Dike in the Field midway hetweeu the 

extreme Eastern and Western Ridges. 

Lens. Similar to the preceding hand-specimens, but rather red- 
dish in color, and somewhat more amvirdaloidal. — Section. A much 
fresher rock thiui' those already described. The few porphyritic feld- 
spars are generally pLagioclase, and cxliibit the same proof of an early 
crystallization mentioned above (i. c. the feldspars of the groundmass 
flow around them, etc.). Tlie feldspars of tlie groundmass are principally 
plagioclase, but some Carlsbad twins and unstriated crystals can be 
fovuid. All these feldspars arc comparatively fresh, and tbo formation 
of tlie greenish scales and other products of decomposition hlis not pro- 
gressed far. Tho frequent inclusions of the original base, however, are 
entirely altered to chloritic products and magnetite. The feldspars con- 
tain occasional large rounded or irregular fluid inclusions, with bubbles, 
and immense numbers of extremely small similar inclusions (requiring 
the use of powers of from 700 to 900) characterized also by occasional 
moving bubbles. Grains and crystals of epidote occur in the feldspars, 
and occasionally (piartz. Chloritic products and magnetite represent the 
original base. Epidote occurs in the groundmass in patches ; calcite is 
rare. True amygdulcs otjcur, fllled with chlorite, quartz, and epidote. 

[8.] From the Ridge constituting the extreme easterly Exposure of the Dike, 
mid not in Line with the Western Half, though trending parallel with it. 

I^ens. A reddish groundmass, containing feldspar crystals, amyg- 
dules of greenish chlorite, and red spots resulting from the dccomposi- 

- il 
I 'I 




tion of the rock. — Section. The least decomposed rock of any exam- 
ined. It has a groundmass composed of small ledge-shaped feldspars, 
magnetite, chlorite, epidote, etc., enclosing porphyritically a few large 
feldspars. The majority of the crystals are plagioclase, but there is a 
considerable number of Carlsbad twins. The small feldspars of the 
groundmass show the flowing of the base around the large crystals, as 
described previously. The larger feldspars contain very characteristic 
inclusions of a base in irregular, reticulated, or cylindrical forms. They 
often fill a large part of the crystal ; may be zonally arranged ; and are 
absolutely identical in shape and other characteristics with the inclu- 
sions of glass or base in the unaltered basalts. These inclusions are now 
altered to magnetite and greenish chioritic or viriditic products. Be- 
sides these dark inclusions of base, the feldspars are filled with almost 
colorless microliths and scales, — the products of the incipient decom- 
position of the fcldspathic substance, — and very minute fluid inclusions, 
rounded, cylindrical, or branching. Some epidote and calcito occur in 
the feldspars. True amygdules arc found, filled with calcite, epidote, 
and chlorite. Irregular masses of epidote occur as areas of alteration in 
the groundmass, — the magnetite often in large masses, enclosing the 


small feldspar crystals of the groundmass, and mixed with considerable 
ferrite. One decomposed crystal may perhaps be referred to olivine. 

[Q. 8'.] 27ie Large Dike running nearly at Right Angles across the Trend 

of the Amygdaloid. 

Lens. A coarse-grained, dark green rock, containing crystals of feld- 
spar, pyrite, magnetite, and hornblende, in a dark green groundmass. 
Section. Contains (comparatively speaking) large-sized feldspar crystals ; 
fibrous, greenish, dichroic hornblende ; crystals of magnetite and pyrite ; 
decomposed crystals of olivine ; epidote ; and viridite, quartz, apatite, 
etc. The feldspars are to a great extent kaolinized. The hornblende 
occurs in irregular masses, shows strong dichroism and brilliant polar- 
ization, and contains a great deal of epidote in rounded grains. Some 
of the feldspar crystals lie imbedded in the hornblende, or cross it, just 
as they do in the case of the augite of the less decomposed diabases, so 
that this and the whole character of the hornblende indicate that it is 
(in part at least) a product of the decomposition of the original augite. 
The olivine occurs generally in shattered crystals, with the usual black- 
ened border. Tlie interior is altered to greenish serpeutiuous products ; 
but little spots still show the polarization and other cliaracteristics of 



the unaltered olivine. The magnetite is found in extremely irregular 
forms, while the pyrite grains often contain magnetite, and therefore 
arise probably from its decomposition. 

[Q. 1'.] One of the Narroiu Dihes rimning i^arallel ivith the Trend of the 


Lens. A compact greenish rock containing crystals of feldspar. 
Section. Contains feldspar crystals, augite, magnetite, pyrite, and do- 
compositiou products. The feldspars arc kaolinizcd, or else decomposed 
to white fibres, and contain considerable cpidote, viridite, etc. The 
augite occurs in irregular masses; it is reddish and has well-marked 
cleavage ; the decomposition to viridite, hornblende, and cpidote is seen 
to be well advanced, these substances forming along the cleavage lines. 
The magnetite often shows the white decomposition characteristic of 
menaccanite. The pyrite is probably derived from the magnetite. No 
traces of olivine were seen. 

[9.] Section of Two Pieces of the Greenish vein-lihe or irregular Masses 

found in the Eock. 

One of the fragments is composed of cpidote, calcite, quartz, and an 
opiuiuc gray substance, perhaps kaolin, — mixed with the remains of 
feldspar crystals. The other fragment, from one of the banded veins, is 
composed of the same substances arranged in bands. Both are proba- 
bly areas of decomposition in the rock. 


From tlie details given we obtain the following generalized description 
of the amygdaloid proper. In the hand specimens the groundmass varies 
in color from green, throiigh gray, to red, — the hast color characteristic 
of the rock that is least decomposed. It sometimes encloses large green 
or white feldspar crystals, often indented by the groundmass, or the feld- 
spar crystals may be comparatively minute ; grains and crystals of cpidote 
arc occasionally seen. The rock generally contains greenish spots of cpi- 
dote and of chloritic material, in part true amygd\dcs, and spots of red- 
dish decomposition. There are also amygdules of calcite and quartz. 

The specimens from wiiich the eight sections were made differ chiefly 
in the degree of decomposition, the presence or absence of olivine, and 
the coarse or fine texture. The specimens from the eastern end are much 
less decomposed than those from the western end. 

I J 

^ I 



As seen under the microscope, tPie rock is composed of large and small 

feldspar crystals, magnetite, epidote, calcitc, and a mass of chlorite, 
viridite, and opacite. The large porphyritic feldspars are twinned plagio- 
clase, and occasionally Carlsbad twins of sanidin. The minute feldspars 
of the groundmass flow around them, encroach upon, and sometimes 
break them. Earely, the groundmass, holding small feldspars, has 
pushed into a crystal, a little distance on either side, and a tongue of 
the (original) base, alone, without the small feldspars, passes through the 
crystal and connects the two intrusions, ~ this connecting tongue now 
altered, however, to calcite, chlorite, and epidote. The small feldspars, 
when sufficiently fresh, show the triclinic twinning; but some Carlsbad 
twins of sanidin and unstriated crystals occm; the former of which 
cannot be referred to the plagioclaso that, owing to the alteration, docs 
not show its multiple twinning. 

The degree of decomposition that the feldspars have undergone varies 
in the different sections : in the freshest rock they contain immense 
quantities of minute fluid inclusions, characterized by moving bubbles, 
and occasional larger ones, rounded or irregular in shape, together with 
inclusions of the base. The latter are cylindrical, or irregularly reticu- 
lated in form, often zonally arranged in the interior or exterior parts of 
the crystal ; they arc absolutely identical in shape, and in their relations 
to the enclosing crystal, with the inclusions of glass or base of the fresh 
basalts ; they are now altered to magnetite, viridite, and other products. 
In the smaller feldspars these intrusions generally run through the 
centre of the crystal, parallel with the twinning-plane. Even in the 
freshest specimens, the substance of the feldspars is filled with minute 
microliths, and scales either colorless or of a light greenish color, wdth 
occasionally some epidote, calcite, or quartz, — generally products of the 
decomposition of the feldspathic substance proper. In the more decom- 
posed specimens these products multiply, so that the crystals become a 
mass of these viriditic scales and fibres (often polarizing with the bril- 
liancy of talc, or in red and yellow colors), or even of opaque kaolin, 
while calcite, epidote, quartz, and colorless needles with cross fracture, 
in part apatite, appear to a greater or less extent The epidote occurs 
generally in the large feldspars in grains : some of it may originate 
from the alteration of included minerals ; but of this there is no proof. 
Occasionally two feldspars interpenetrate each other. 

The only other original mineral, unless it be part of the magnetite and 
apatite, is olivine. This was found in well-marked, large, and undecom- 
posed crystals only near the contact of the amygdaloid with the con- 




glomerate (described with section [2] ) ; though what seemed to be the 
remains of olivine crystalis were found in one or two other sections. 
Their relations to the groundmass prove an anterior origin : some of the 
magnetite and opacite in the sections have probably been derived from 
the alteration of small fragments of olivine. 

Between the lafgc and small feldspar crystals lies a mass of greenish 
alteration products, — chlorite (often dichroic), viridite, magnetite, opa- 
cite, considerable cpidoto, quartz, and calcite. When some of the large 
feldspar crystals diverge, the triangular space between them is filled 
with very small feldspar crystals, lying in this greenish mass ; showing, 
as has been often remarked, that it is merely an original, glassy base, 
much altered, for we find this same relation in the unaltered basalts. 
Calcite, quartz, epidote, hornblende, biotite, apatite, etc., in |;he decom- 
posed base, seem to belong to the more advanced state of decomposition. 

Magnetite is always present. A large part of the magnetite arises 
from the decomposition of the base, and it is generally difiicult to say 
what part of it is original. 

While in some sections true amygdules are wanting, yet they gener- 
ally occur, characterized by their sharp boundary, and the arrangement 
of the feldspars of the groundmass parallel to their outline. They are 
filled by epidote, chlorite, viridite, calcite, or quartz; the epidote gener- 
ally on the outside, when other minerals occur with it. Besides these true 
amygdules, ai'cas of decomposition occur in the groimdmass, consistiuf*- 
either of opaque ferritic material, constituting the macroscopical red 
spots, or of epidote, chlorite, viridite, etc., enclosing the small feldspars. 

Assuming that all the specimens described belong to the same rock- 
mass, this rock, according to the classification used, would be referred 
to both the Diabase and Melaphyr sections of the Basalts* (according to 
the specimen examined), or again might be called a Diabase and Olivine- 
diabase.t It is found by study to be a rock which, in the original state, 
was composed of the feldspars, olivine, magnetite, a base (glassy, micro- 
lithic, etc.), and probably some augite (though this cannot be identified 
now), all in varying proportions, and that these original constituents 
have been largely replaced by secondary products. It is therefore an 
altered basalt, as has been previously shown by others for similai- rocks 
of this region. J 

* M. E. Wadsworth "On the Classification of Rocks," Bulletin Mus. Comp. Zool., 
Vol. y. No. 13. 

t Rosenbusch, Mikros. Phys. der Mass. Gest., etc. 

.t M. E. Wadsworth, Proc. Bost. Soc. I^at. Hist, Vol. XIX, p. 217 et scq., 1877. 
E. R. Benton, Ibid., Vol. XX. p. 41G et seq., 1880. 
VOL. VII. — NO. 7. 16 


The examination of the sections made from some of the narrow dikes 
which cut the amygdaloid seems to show, in general, a simdarity to 
either [Q. I'l or [6] - one series containmg undccomposed angite, the 
other none that can be identified. The great cross dike is descnbed 
under [Q. 8']. All of these later eruptive rocks seem in a more advanced 
stage of decomposition than the amygdaloid. 

July, 1882. 

No. 8. 

On some Specimens of Permian Fossil Plants from Cola 

rado. By Leo Lesquekeux. 

Last February, Eev, Arthur Lakes, of Golden, wrote me that he had 
found in South Park, near Fairplay, Colorado, a bed of shale with 
beautiful insect remains mixed with a profusion of vegetable fraf^tnents 
resembling the scales and seeds of Conifers, and with them some well- 
defined forms, among others a small stem of Lepidodendron^ showino- 
distinctly the scars and various small branches of Conifers, or Zaniia? or 
LycopodiacGDO. "Those remains," he said, "are in the Eed-bods, on an 
horizon appearing to us when examining the locality as Lower Triassic, 
or Permian, or Carboniferous. A thin scam of coal was also discovered 
adjacent to the beds, and one tiny shell." 

Some time later Mr. Lakes sent me a box of specimens from the local- 
ity mentioned above, asking me to determine them if possible, to report 
to him what evidence on the age of the formation could be derived from 
these vegetable remauis, and to send the specimens to the Museum of 
Comparative Zoology at Cambridge. 

Though i\\Q specimens are very small, covered with mixed minute 
fragments of leaves, scales, flowers, and seeds of Conifers, leaflets of Ferns, 
etc., I was able to recognize, in all those which could be determined, the 
characters of a Permian vegetation, and I reported to Mr. Lakes ac- 

Being then about to publish the list of the determined species, with 

some remarks upon them. Prof. Samuel Scudder, to whom the insects had 

been sent, advised me that, from the characters of the animal remains, 

his conclusions on the age of the formation did not fully agree with those 

derived from the plants. As he was going to examine the locality 

himself, ho wrote me that ho might perhaps fmd some more valuable 

specimens, and that ho would communicate them to mo when returned 

These specimens, kindly communicated by Prof, Scudder, were re- 
ceived two weeks ago. Though the vegetable remains preserved upon 
them are quite as broken, mixed, and indistinct as those of Mr. Lakes, I 
found a few of them whose determination added some new evidence to 
that wln'ch had been procured already. 

VOL. VII. —NO. 8. 



The species which T consider as positively determined from all the 

specimens arc the following : 

1. Collection of the Musemn of Comparative Zoology, 

Calamarite. — S'phe'iiophyllum SchlotheimM'Qr.^ an entire perfectly preserved 
whorl. No. 1 of the collection. 

Ferns. — donio'ptcris ohtudloha Naum. Nos. 2 and 4. 

Ncuropteris Losohii Br,, or Cydopteris cordata Gocpp. No. G. 
Fragment of an Aldliopteris lilvc A, lingulcUa Goei)p. No. 7\ 
Five specimens of fragments of small leailets of Ferns, not determinable. 

No. 18. 
Lycofodiace^. — Leaves of Lepidodendron. No. 0. The stem of Lcpidoden- 
dron recorded by Mr. Lakes, and rightly described by him in his letter, 

was not found in the collection. 
Conifers. ^ Seeds of Ulhrhfonnia selaginoides Gein., LeilpQ. No. 8. 
Scales or involucres of Wcilclbia \ linearifolia ? Goepp. No. 10. 
Young leaves of Ull/mannia Bronnii Goepp. No. 11. 
Leaves (detached) of U. friimentaria Goepp. Very abundant, and mixed 

with those of U. Bronnii. No. 12. 
Leaves of U. selaginoides Gein. No. 13. 
Branches bearing leaves of Walchia piniformis St. No. 14. Abundant 

and variable. 
Fra.gments, mostly ground nearly to powder, of leaves, flowers, and seeds of 

Ullmannia Walchia, etc. Nos. 15 and IG. 

Branch of Ullmannia Bronnii Goepp. No. 17. 

2. Collection of Prof. Scudder. 

CALAMARiiH;. — S plimophjllum cmarginatum Br. No. 9. Good specimen. 

l^ragment of racliis with a few leaves of Sphmophyllimi species, Gein., as 
figured in Nachtr. zur Dyas, L, Ph L fig. 22. 
Ferns. — Schizopteris species. Same as figured in Gein., Ibid., PI. I. figs. 18, 

18^ No. G. 
Sphenop>teris (kiniizii Goepp. No. 7. In many specimens. 
Ilijrrienoplujlllks Lcncharii Gcln. No. S. 
Cydopteris rarinerimc Goepp. No. 10. 
Splbenopteris eoriacea'^ White & Font. No. 11. 
Gonioptens Ncv;herriana 1 Wiute & Font. No. 12. 
reeopteris arhorcscens Brgt., in fruit. No. 13. 
CjjdJkdtes Beyriclii Weiss. No. 14. 
Callipleris conferta ! var. ohlupia ? Weiss. No. 15. 
Sphenoptcris deniala ? White & Font. Nos. 15'' and IG. 
Small fragments of Ferns indeterminable. Nos. 17, 18. 
LYCoroDiACEiE. — L GpidophjlluTfi species. Sporangc and blade. No. 5. 




2 A n 

Conifers. — Leaves of WalcJiia lomjifoUa Goepp. No. ^0. 

Leaves of AhUiites Goepp. Fragments iu many speeiniens. ISTo. 21. 

Leaves of Ulhiiannia fnimentarla Goejip., and IL Bronnii, No. 1, abouiid. 

Brauchea and leaves of JValchia piniformis, No. 3, in, plenty of .specimens. 
CoRDAiTE^g. — Cordailes horasdfulius ling-. Very line speciuicn. No. 4. 

Fragments of leaves of Oordaites species. No 22. 

CanUocarpits orbicularis Gtiepp. No. 24. 

Cardiocarpns species nov., allieil to C. gihberosus Gein. No. 25. 

Carpolilkes species, one referable to G. hamidus Ileer, the other, very 
small Ijut in ])lenty of specimens, to 0. Geinitzi Heer, Perm. PlI. of 
Funkirchen, Fl. XXIl. figs. 5, G, 7, 8, and 13. These are all mixed 
■with ground fragments of scales, leaves, etc. of JValchia and Ullmanuia. 
No. 26. Sanre as No. 16 of the colleclion of the Museum of Comparative 

On tho above species of vegetable remains I add a few remarks in 
regard to their evidence for the determination of the age of the forma- 
tion where they have been found. 

The genus Sphenophj/llam ruugcs from the Silurian to the base of the 
Permian, as far as known, at least, by tho present state of our knowl- 
edge in vegetable palaeontology. Tln-ee species of the genus are recorded 
by German authors, as from the Permiau : Sphenojihyllum Schlotkeimii, 
S. emarginatum, and S, loiigifoUmn. But all ai'e from the lower strata 
of tho Old Eed Sandstone, whose flora is so intimately connectetl by its 
characters with that of the Upper Carboniferous that the exact limita- 
tion between the formations has not been fixed. It is tho same with 
the Permo-Carboniferous strata of Virginia, wlierefrom a number of spe- 
cies of SpheiiopJu/llam are described by White and Fontaine. Here we 
are not yet in the true Permian. A very small and obscui'c fragment of 
a Sjjhenophylkmi species is described by Geinitz, Naclitr. zur Dyas, L, 
p. 10, PL I. figs. 22, 23. It is as yet the only trace of the genus in 
the Middle Permian. The specific characters are not discernible, and 
the author remails that he 1ms published it only because it is as yet tho 
only species of Sj'heuophyllam found in tlie Permian of Germany, The 
presence of two species of this genus in the s])cciLuons of Fairphiy' would 
be already sufficient authoi-ity for referring tho formation to the paleo- 
zoic time. 

In the Ferns, the s])ecimens represent Nenropteris Lim-hii, a species 
found already in the whole thickness of the Carboniferous, and also in the 
Permian of Europe. Pecoptevis arhoremim, Upper Carboniferous and 
Lower Permian. Gallipteris covferia, one of the more abundant species of 
the Permian in Europe, and found until ngw on this continent only in 



the Permo-Carbonifcrous beds of Virginia. dontopteris ohtitsiloha^ Cy- 
clopteris rarineyirls, Odoniopteris cordata which is scarcely distinguishable 
from Neuropteris Loschii^ Cyatheites Schhtheimii var. latifolia^ Sphenopteris 
Gehiitzi, Ilymenophyllitcs Leuckarti, as well as a Schizoj)teris, are all Per- 
mian species only. The other named species of Ferns are uncertain on 
account of the insufficiency of specimens, but they are referable to types 
of the Permian or Permo-Carboniferous. 

In the Conifers, the most abundantly represented in the specimens 
of Fairplay are the two more distinctly characteristic of the Permian, 
Ullmannia friimentaria '<xxi(\ Walchia piuiforviis. There are besides nu- 
merous leaves and branches of Uknannia Broiiniij and leaves of U. selagi- 
noides, of Walchia lowjifolia, and of AUetites, species all representatives 

of the same formation only. 

In the Lycopodiacea), Mr. Lakes has found a branch of Lepidodendron 
which I have not seen among the specimens, but two of them have frag- 
ments of leaves of tins genus, and a Lepidophyllum Avith blade and spo- 
range. It is well known that the Lycopodiaccoe disappear at the base of 
the Trias, or rather in the Upper Permian. The same can be said of the 
Cordaites, of which G. horassifolius is represented upon the largest frag- 
ment of shale I have seen from Fairplay. 

The age of a flora is indicated, not only by the presence of certain 
types, but by the absence of otiiers. And in this, the group of vegetable 
remains in Fairplay is remarkably free of any fragments of plants char- 
acterizing the Triassic period. There is no trace of Equisetaceai or of 
Cycadea). The fragments doubtfully referred to Cycas by Mr. Lakes in 
his letter are all leaves of Ullmannia friime?itaria and U. longifolia. 
The Ferns are of a totally different character also. Prof William Fon- 
taine has prepared a memoir, descriptions, and figures of a large num- 
ber of species of plants obtained from the so-called Triassic measures of 
Virginia, which he considers as the equivalent of the PJietic of Europe. 
On these plants, Prof Fontaine writes me that none of them could be 
referred to the Permian, or to any of the species which I have recorded 
from tho specimens of Fairplay. 

Possibly these Permian fossil remains will help to determine the geo- 
logical distribution of the strata of South Park. In Dr. F. V. Hayden's 
Animal Report of 187.'?, Dr. A. C. Pcale gives a section of the valley 
from Platte River to Trout Creek, on a distance of six miles. The sec- 
tion passes about five miles north of Fairplay. Its lower part, or beds 
No. 18 to 50, represent an open series of 1,250 feet of strata, all hypo- 
thetically referred by Dr. Peale to the Carboniferous or Permian, for no 





fossils of any kind were found to prove it. Above tins there is a covered 

space (beds ^o. 51 and 52) of 1,300 to 1,500 feet, which is referred to 

the Ked-beda or Triassic. The whole is covered by a thickness of Jurassic 

strata, overlaid by about 2,000 feet of Cretaceous. From this it appears 

very probable that the remains of 2:)lants found by Rev. Mr. Lakes first, 

and after him by Prof. Scudder, represent part of the first scries of beds 

No. 18 to 50, all exposed and as yet hypothctically referred by Dr. 

Pealo to the Carboniferous and the Permian. The exact location of the 

plant-bearing beds in the section of Dr. Peale may probably be easily 

October, 1882. 




No. 9. — On the Relations of tJie Triassic Traps and Sandstones of 

the Eastern United States. By William Morris Davis. 

1. Introductory. 

2. Literature. 

3. Observations. Nomenclature. — A, Turner's Falls. — B, Mount Tom. — C, 

West SpringMd, Mass. — D, Beckley Station. ~ E, Mcriden. — F, Walling- 
ford. — G, New Haven, Conn. — II, Fort Lee and Englewood, — J, Weohawken, 
— K, Jersey City. — L, Paterson and Little Falls. — M, Feltville. — N, Mar- 
tin's Dock. — 0. Point Pleasant Station. — P, Lambert ville, K. J. 

4. Brief Statement oe Former Views. 

5. General Discussion. Origin of the Triassic Estuaries and Cause of Trap Erup- 

tions ; Origin and Deposition of the Strata ; Composition of the Trap ; Kelations 
of the Trap and Sandstone ; Eeview of Previous Ideas ; Test-Characters for In- 
truded and Overflow Sheets ; Examples of these elsewhere; Dikes; Intrusions; 
Overflows; Amygdaloida; Elfect of Trap on Sandstones; Tilting; Theories to 
account for the Monoclinal Structure ; Faults ; Folds. 

6. Summary, 


Since seeing in 1877 the trap conglomerate on the back of Mount 
Tom, I have doubted the generally accepted explanation of the intrusive 
orighi of the Triassic traps, and inclined to Hitchcock's theory of their 
origin by overflow contemporaneous with the deposit of the sandstone. 
During the past summer the desired opportunity came to examine the 
question further, by personal observation, in Massachusetts, Connecticut, 
and New Jersey, as detailed below, and with the result of satisfying my- 
self that both views are correct; that some of the trap sheets are of 
intrusive, and some of overflow origin. The Palisade range along the 
Hudson may be taken as the type of the first, as has been shown by 
Rusaell ; Mount Tom in Massachusetts represents the second, as was 
shown by Hitchcock. Other examples will be found below. 

My endeavor has been to discover critical points that give decisive 
evidence one way or the other as to the origin of the trap sheets, so as 
to compel instead of merely allowing an explanation ; but observations 
satisfactory or compulsory to one observer arc not always so to another, 
and I cannot, therefore, expect that wliat has convinced me will surely 

VOL. VII. — no. 9. 



be equally convincing to those who have thought differently; but to 
those who agree with my conclusions, as well as to those who differ from 
them, I would quote the wish of the elder Silliman : " I take the liberty 
to request, that those who may have it in their power will make precise 
observations upon the appearances at the junctions, .... accompanied 
by drawings and specimens when it is convenient ; and at least with 
accurate descriptions. We might thus be in a condition to form a 
general opinion of the origin of our trap rocks." * 


A number of unimportant references to the Triassic rocks in Annual 
Reports of State Surveys are omitted in the following list. These can 
easily be found, if desired, by following Prime's "Catalogue of Official 
Ecports," etc., in the Trans. Amer. Inst. Mining Engineers, VIL, 1879, 
455. Papers referring only to fossils and date of the deposits are also 
omitted, as the question of the age of the strata, for which the generally 
accepted determination is adopted, does not now arise. Picferences to 
the articles cited are made in the text below simply by page number if 
the author has but one title in the list ; by letter and page number, if 
several of his papers arc given. Pages in parentheses after a title show 
that only those pages of the paper are devoted to the Triassic formation. 
Papers that have not been seen are marked with an asterisk. 

Akerly, S. 

The Geology of the Hudson Kiver. New York, 1820, (25-39, 57-64), and 


Canada Geol. Surv., 

Alger, F. See Jackson and Alger. 
Bailey, L. W., and Matthew, G. F. 

Preliminary Report on the Geology of Southern New Brunswick. 
GeoL Surv., 1870-71, (216-221). 

Bailey, L. W., Matthew, G. F., and EUs, R. W. 

Ilej)ort on the Geology of Southern New Brunswick. 

1878-79, (21-23 D), maps and sections. 

Bailey, L. W., Matthew, G. F., and Hartt, C. F. 

Observations on the Geology of Southern New Brunswick. Fredericton, 
1865, (123-125), map and sections. 

Barratt, J. 

On the Evidence of Congelation in the New Red Sandstone. Assoc. Amer. 
Geols. Proc, 1845, 26. 

* Amer. Joura, Sci., XVXI., 1830, 131. 


p ■ 



> J 

Bradley, F, H. 

On a "Geological Chart of the United States," etc. A. J. S. [3], XII., 

1876, (289). 

Britten, N. L. 

On the Geology of Richmond County, New York. N. Y. Acad. Sci. Ann., 
II., 1881, (168-170), map and sections. 


Atlas to Geology of Canada. Montreal, 1863, 

Chapin, A. B. 

Junction of Trap and Sandstone ; "Wallingford, Conn. A. J. S. [1], XXVII. , 
1835, 104-112. 

Cleaveland, P. 

An Elementary Treatise on Mineralogy and Geology. 2d Edition. Boston, 

1822, (746, 759). 

Clemson, T. G. 

Notice of a Geological Examination of the Country between Fredericksbui^ 
and Winchester, in Virgniia, including the Gold Region. Penn. Geol. 
Soc. Trans., I., 1835, (311-313). 

Cook, G. H, 

a. Geological Survey of New Jersey. Map of the Triassic Formations. 

6. Geology of New Jersey. Newark, 1868, (173-238, 336-339). 

c. Geological Survey of New Jersey. Annual Report for 1879. Trenton, 

1879, (18-35). 

d. Geological Survey of New Jersey. Geological Map of New Jersey. 


Cook, G. H., and Smock, J. C. 

Geological Survey of New Jersey. Report on the Clay Deposits, etc. 

Trenton, 1878, (170, 301-306). 

Cooper, T. 

On Volcanoes and Volcanic Substances, with a particular Reference to the 

Origin of the Rocks of the Floetz Trap Formation. A. J. S. [1], IV., 

1822, (239-243), 

Credner, H. 

Geognostische Skizze der Umgegend von New York, Deutsch. Geol. Gesell. 

Zft., XVIL, 1865, (392-394). 
Dana, E. S. 

a. Abstract of a Paper on the Trap Rocks of the Connecticut Valley, A. 

J. S. [3], VIII., 1874, 390-392. 
6. Trap Rocks of the Connecticut Valley. Amer. Assoc. Proc, 1874, 





Dana, J. D. 

a. Origin of the Grand Outline Features of the Earth. A. J. S. [2], III., 

1847, (390-392). 

6. Manual of Geology. Philadelphia, 18G3, 18G9, (21, 414-443). 
C. The same. New York, 1870, 1880, (21, 403-423). 

d. On the Geology of the New Haven Eegion, with special Reference to the 
Origin of some of its Topographical Features. Conn. Acad. Trans., II., 
1871-73, (45-48). 

e. On some Results of the Earth's Contraction from Cooling ; Part IV. 

Igneous Ejections, Volcanoes. A. J. S. [3], VI., 1873, (104-113). 

/. Notes on Percivars Observations on " Indurated Bitumen " in the Con- 
necticut Trap. A. J. S. [3], XVL, 1878, 130-132. 

g. (On Eussell's " Physical History," etc.) A. J. S. [3], XVII., 1879, 

Dawson, J. W. 

a. On the New Red Sandstone of Nova Scotia. Geol. Soc. Journ., IV., 

1848, 50-59, map and sections. 

6. Additional Notes on the Red Sandstones of Nova Scotia. Geol. Soc. 
Journ., VIII., 1852, 398-400. 

c. On the Parallelism of the Rock Formations of Nova Scotia with those of 
other Parts of America. Amer. Assoc. Proc, X., 1856, (20, 21). 

<f. Acadian Geology. Edinburgh, 1855, (60-115). 

e. The same. London. 2d Edition. 1868, (86-124). 

/. Notes on the Geology of Prince Edward Island in the Gulf of St. Law- 
rence. Geol. Mag., IX., 1872, (203-205). 

g. The Physical Geography of Prince Edward Island. Canad. Nat., VIL, 
1872, 342, 343. 

h. Supplement to the Second Edition of Acadian Geology. London, 1878, 

Dawson, J. W., and Harrington, B. J. 

Report on the Geological Structure and Mineral Resources of Prince Ed- 
ward Island. Montreal, 1871, (13-21). 

Eaton, A. 

a. An Index to the Geology of the Northern States. Leicester, 1818, 

, h. The same. 1820, (206-212, 215-221, 249-256). 

c. A Geological Nomenclature for North America. Albany, 1828, (section). 

Ells, R. W. See Bailey, Matthew, and Ells. 

Emerson, B. K. 

The Deerfield Dyke and its Minerals. A. J. S. [3], XXIV., 1882, (195, 196). 

Emmons, E. 
■ a. Notice of a Scientific Excursion (to Nova Scotia). A. J. S. [1], XXX., 
1836, (334-338). 







Emmons, E. 

6. Agriculture of New York. Albany, 1846, I., (200, 201). 

c. American Geology. Albany, 1854, (106-112). 

d. Geological Kcpoi-t of the Midland Counties of North Carolina. New 
York, 1856, (227-342), map and sections. 

e. The Chemical Conatitution of certain Members of the Chatham Series in 
the Valley of Deep River, North Cai'olina. Amer. Assoc Proc, XII., 
1858, 230-232. 

Fontaine, W. M, 

Notes on the Mesozoic Strata of Virginia. 

151-157, 229-239. 

A, J. S. [3], XVIL, 1879, 25-39, 

Frazcr, P., Jr. 

a. Second Geological Survey of Pennsylvania. Report of Progress in the 

District of York and Adams Counties, etc. Hariisburg, 1876, map and 

6. The same. Report of Progress in the Counties of York, Adams, Cum- 
berland, and Franklin. Harrisburg, 1877, map and sections. 

c. The same. The Geology of Lancaster County. Harrisburg, 1880, with 

a volume of maps. 

d. The Position of the AToerican New Red Sandstone. Amer. Inst. Mining 

Engr. Trans., V., 1877, 494-501. 

e. Regarding some Mesozoic Ores. Amer. Phil. Soc. Proc, XVI., 1877, 


/. The Mesozoic Sandstones of the Atlantic Slope. Amer. Nat., 1879, 


Gcsner, A. 

A Geological Map of Nova Scotia, with an 

Geol. Soc. Proc, IV., 1846, (190). 

accompanying Memoir [1843]. 

Gibson, J. B. 

Observations on the Trap Rocks of the Connewago Hills, .... Pa. [1320]. 

Amer. PhiL Soc, II., 1825, 156-166. 
Harrington, B. J- See Dawson and Harrington. 
Hartt, C. F. See Bailey, Matthew, and.Hartt. 

Hawes, G. W. 

a. The Trap Rocks of the Connecticut Valley. A. J. S. [3], IX., 1875, 

h. On the Mineralogical Composition of the Normal Mesozoic Diabase upon 
the Atlantic Border. Washington Nat. Mus. Proc, 1881, 129-134. 

Heinrich, O. J. 

The Mesozoic Formation in Virginia. Amer. Inst. Mining Engr. Trans., 
VL, 1879, 227-274, map and sections. 



Hitchcock) B. 

a. Kemarks on the Geology and Mineralogy of aSection of Massachusetts, 

on Connecticut Kiver, with a Part of New Hampshire and Vermont. 
A. J. S. [1], I., 1818, 105-116, map and section. 

5. A Sketch of the Geology, Mineralogy, and Scenery of the Regions con- 
tiguous to the River Connecticut, with a Geological Map, etc. A. J. S. 
[1], YL, 1823, (39-80), map and sections. 

c. Miscellaneous Notices of Mineral Localities, with Geological Remarks. 
A. J. S. [I], XIV., 1828, (227, 228). 

d. Report on the Geology, Mineralogy, Botany, and Zoology of Massachu- 
setts. Amherst, 1833, (206-241, 404-439), map and sections. 

e. Final Report on the Geology of Massachusetts. Amherst, 1841, (19&- 

204, 434-531, 640-663), map and sections. 
/. On the Trap Tufa or Volcanic Grit of the Connecticut Valley, etc. Assoc. 

Amer. Geols. Proc, 1844, 10, 11 ; A. J. S. [I], XLVIL, 1844, 103, 104. 
g. Description of several Sections measured across the Sandstone and Trap 

of the Connecticut River Valley in Massachusetts. Amer. Assoc. Proc, 

IX., 1855, 225-227. 
h. Ichnology of New England. A Report on the Sandstone of the Con- 
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Jackson, C. T. 

a. Nature of Minerals accompanying Trap Dykes which intercept various 

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Nat. Hist. Proc, VI., 1856-59, 30-34. 

Jackson, C. T., and Alger, F. 

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6. Remarks on the Mineralogy and Geology of Nova Scotia. Amer. Acad. 

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Kerr, W. C. 

a. Observations on the Mesozoic of North Carolina. Amer. Assoc. Proc, 

1874, 47-49. 
6. Report on the Geological Survey of North Carolina. Raleigh, 1875, 

(141-147), map and sections. 

Leconte, J. 

Elements of Geology. New York, 1878, (43^U7). 

Lesley, J. P. 

a. Manual of Coal and its Topography. Philadelphia, 1856, (132, 133). 

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Ueber, O. M. 

Reports on the Geognostic Survey of South Carolina. Columbia, 1860, 

(19, 20), map. 




Lyell, Sir C. 

a. On the Fossil Footprints of Birds and Impressions of Eain-drops in the 

Valley of the Connecticut. Gcol. Soc. Proc, III., 1842, 793-79G. 
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c. On the Structure and prohahlc Age of the Coal Field of the James River, 
near Richmond, Virginia, Gcol. Soc. Journ., III., 1847, 2G1-280. 

d. A Second Visit to the United States. New York, 1849, (I. 211-217). 

e. On Fossil Rain-marks of the Recent, Triassic, and Carhoniferous Periods. 
GcoL Soc. Journ., VIL, 1851, 238-247. 

Macfarlane, J. 

The Coal Regions of America. New York, 1873, (505-528). 

Maclure, W. 

a. Observations on the Geology of the United States, explanatory of a 
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h. On the Geology of the United States of North America, etc. Philadel- 
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Martin, B. N. 

(On the Trapoid Rocks of the Palisades.) N. Y. Lyceum Proc, I., 1870- 
71, 132, 133. 

Mather, W. W. 

Geology of New York. Part I., comprising Geology of the First Geological 
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Matthew, G. F. See Bailey and Matthew. 

Mitchell, E. 

Elements of Geology, with an Outline of the Geology of North Carolina. 
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Newberry, J. S. 

Genesis of Sandstones. N. Y. Lyceum Proc, L, 1870-71, 131. 

Olmsted, D. 

a. Red Sandstone Formation of North Carolnia. A, J. S. [1], IL, 1819, 
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Account of the Geology, Mineralogy, Scenery, etc of the Secondary Region 
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Percival, J. G. 

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. (I 

State of Connecticut. New Haven, 1842, 



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1842, 25. 

e. (Origin of the Crescent Form of the Triassic Dykes.) A. J. S., XLV,, 

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/. Address. Assoc. Amer. Geols., 1844, (27-31). 

g. The Geology of Pennsylvania. 1858, (II. 666-697, 769-765), map and 

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h. Report of the Progress of the Geological Survey of the ^t^te of Virginia 
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1842, 26, 27, 28. 

d. On the Age of the Coal Rocks of Eastern Virginia. Assoc. Amer. Geols. 

Proc, 1843, 298-316. 

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Russell, I. C. 

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A. J. S. [3], XV., 1878, 277-280. 
6. On the Occurrence of Solid Hydrocarbons in the Eruptive Rocks of New 

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c. Analyses of Sandstones from New Jersey. N. Y. Lyceum Proc, I., 





Schweitzer, P. 

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Silliman, B., Jr. 

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Assoc. Amer. Geols. Pmc, 1844, 14, 15 

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a. Memoir of a Section passing through the Bituminous Coal Field near 
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VOL. VII. — NO. 9. 17 


, r 





Walling, H. F. 

Some Indications of Recent Sensitiveness to Unequal Pressures in the 

Earth's Crust. Amer. Assoc. Proc, XXVII., 1878, 190-197. 

Whelpley, J. D. 

Trap and Sandstone of the Connecticut Valley, — Theory of their Relation. 

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The following observations were made in the summer of 1882. The 
attempt has been made in recording them to keep inference distinct 
from observed fact, though the two may come in the same sentence. 
The observations have been reduced as far as possible to graphic form, 
for ease of reading as well as for the convenience of those who may care 
to repeat them. It should be remembered that they are mostly the 
work of short excursions, made with the object of discovering the posi- 
tion and condition of the rocks only at certain points, and not with any 
idea of preparing complete geological maps of a district. The plans are 
generally traced from topographical or geological maps; none of the 
sections are constructed accurately, but all are kept down near natural 
proportions. In order to avoid too much assumption in these sec- 
tions, all lines of contact not directly seen are drawn broken-dotted 

( )j the Hanging Hills section is an accidental exception to 

this rule. The scales of maps and sections are only approximate. The 
observations are referred to in the text farther on by the letters at 

tlicir headings. 

Fomendature. — The trap ranges are grouped according to Pcrcival's 
method : the .largest of a system is called the 7nain range; lateral ranges 
on the outcrop side or face of the main range are called anterior; on the 
back or dip side, posterior. These lateral ranges are numbered accord- 
ing to their distance from the main range. In the case of overflows, 
these terms have the imforcseen advantage of serving to denote the rela- 
tive dates of eruption. Upper and lower contacts arc between the trap 
and the overlying and underlying sandstones. Dike (except in quota- 
tions) is restricted to masses of igneous rock clearly of later date than the 
rocks they intersect, and with a greater extension across the layers of 
sandstone than parallel to them. Sheet is applied to intcrbodded masses 
of trap, of intrusive or of overflow origin. Sandstone is sometimes used 






in a general sense, applying to the whole formation, and is then not 
closely limited to its lithologioal meaning. Bearings are all magnetic. 
Fage references to previous writings are made in parentheses after the 
author's name ; the titles are given in the list above. 

A. Turner's Falls, Mass, (figs. 32, 33, 34). — This manufacturing 
town is on a corner of land on the left bank of the Connecticut, which 
here makes a considerable detour from its usual course, and on the way 
exposes an excellent continuous section of sandstones and trap for more 
than a mile. This is best examined by beginning on the northwestern 
bank, one eighth of a mile below the lower suspension bridge (A, fig. 32), 
where the back of the main trap range is clearly seen. This range has 
its beginning on the southwest flank of Mount Toby in Sunderland, in 
a layer of trap making an inconspicuous ridge; Hitchcock has de- 
scribed its upper contact with sandstone in a brook a mile and a half 
southeast of Sunderland. It then advances northwest, and ascends on 
the back of Dccrfield Mountain, gaining the summit a few miles before 
the Deerfield Elver outs through the ridge to the Connecticut; two 
railroads pass through this gorge and cut the trap, but do not, so far as 
I could see in passing, show any contacts. East of Greenfield the Poet's 
Seat is the culminating point ; here the ridge is doubled, with a shallow 
valley along its top, probably indicating a bed of sandstone or tufa, or a 
strike fault. It is the upper surface of this main trap sheet that comes 
to the river's edge below Turner's Falls (A, fig. 32); and going up 
stream the Ijright red shaly sandstone is soon met lying upon its vesic- 
ular, amygdaloidal surface, quite conformable to its slight irregularities, 
and showing no signs of local baking at the junction, or of any branch- 
ing intrusions from the trap below. The sandstone strikes N. 66° E., 
dips 35° S. E. throughout the section. Following up the bank, we pasa 
obliquely across the strike of the sandstone, and just before coming to 
the bridge reach the first posterior trap (B). The contact is unfortu- 
nately hidden here ; it might be found by searching on the face of this 
posterior ridge farther northeast. The trap is at first dense, but a little 
beyond the bridge becomes vesicular, and so continues up to the en- 
trance of Fall River. Looking southwest across the river, one may see 
an outcrop of rocks about in line with the strike of this trap, but they 
seem to be bedded ; no ridge is visible in that direction, and I believe 
the trap ends about where the river crosses it. Going up stream the 
trap is seen continuously except in two places where covered by sand- 
stone : the first is in a little hollow on its back (C), about one third of 
the way to the mouth of Fall Kiver, where the bedding of the sandstone 



is somewhat uneven, bi j not more so, I imagined, than would Yesult 
from the washing in of sand and mud to fill an irregular hollow ; this 
exposure is about twenty feet square ; the second is a much larger trian- 
gxilar patch of sandstone (D) at the mouth of Fall Eiver, giving excel- 
lent contact specimens, very little weathered, retaining the usual texture, 
softness and color of the sandstone directly to the trap surface, and 
holding small scraps of trap clearly separated from the mass below (see 
fig. 34). A wooden dam gives passage across Fail Hiver near its 
mouth, and directly opposite (S. E.) there is a small exposure of sand- 
stone overlaid by trap breccia, with contact hidden. Farther up this 
valley, by climbing up its steep southeast bank opposite a road bridge, 
a larger exposure (E) is found some eighty feet over the stream. The 
sandstone is gray and micaceous, and dips a little steeper than usual; 
its contact with the igneous rocks is hidden, but after a blank of say 
five feet there is a bank of tufa containing fragments of hard trap. The 
tufa is deeply weathered, so that I could got no good specimen with 
fresh surface ; it shows parallel lines on its weathered front, which seem 
to indicate bedding, as they were conformable with the sandstone strata 
below. The trap fragments here are round or oval, not angular as by 
the dam ;' some are as much as two feet in diameter, with a hard, dense 
surface, but vesicular within ; they may be volcanic bombs. Twenty 
to thirty feet will probably cover the thickness of this tufa bed ; next 
comes the dense trap of the second posterior range, well exposed at its 
southern end in a rocky point on the river bank; passing around this, 
we come to the third exposure (F) of overlying sandstone, showing the 


same features as the first. This trap also is not apparent as a ridge 
farther southwest, but points to a sandstone island in the river, and 
may, like the first posterior ridge, end about where the river cuts it. 
From here up to the falls, one fourth of a mile, beds of shale, sandstone, 
and conglomerate are well exposed in ascending section, but no more 
trap appears. The close conformity of the trap and sandstone through- 
out this series is noticeable. 

This section is described and figured by Hitchcock (d, 423; e, 653, 
here copied, fig, 7). Numerous specimens of foot-prints have been 
found in the neighborhood. Emerson's recent article on the Deerfield 
Dyke and its minerals appeared after the above description was written: 
it confirms the overflow origin of the trap, but speaks of only two trap 
ridges, and regards these as originally one, now separated by a fault in 
the Fall River valley. I do not consider the evidence offered in favor 
of this view as fully excluding the idea of separate overflows of limited 



area, 'as above suggested ; although, so far as the origin of the trap is 
concerned, it is immaterial whether the ridges are regarded as a single 
sheet faulted or as separate shccta. 

B. Mount ToTTij Mass. (figs. 35, 36, 37). ^This section is one of the 
best I have seen. The following description is reversed from the de- 
scending order in which the observations were made. The bench on 
the western face of the mountain below the talus of trap fragments ia 
dependent on a hard sandstone conglomerate; it forms a ridge by itself 
from the southern end of Tom over two miles to Rock Valley, whore it 
dies away. The rock quarried at Mount Tom Station, Connecticut River 
Railroad, seems to be of the same horizon. From this bench the sand- 
stone is generally hidden by trap blocks ; but about three quarters of a 
mile north of the end of Mount Tom, there is a small exposure of sand- 
stone in contact with the great trap cover; others doubtless occur, but 
on finding this one I searched no farther. The sandstone here, a few 
feet from the trap, is gray, micaceous, and clearly bedded ; but near and 
at the contact it is dense, as hard as quartzite, bluish, and somewhat 
like the trap itself in appearance, with only the larger bedding-joints 
remaining. The two rocks are not welded together here : an open seam 
separates them, so that no single specimen shows both. The trap is 
dark, dense, fine-grained, and excessively hard; it lies evenly on the 
layers below without cutting them; the columnar strs .ture does not 
show for some ten foot higher. 

of the r(pck is much coarser, the crystals are occasionally a tenth of an 
inch in length. Descending the long eastern slope by a wood road, there 
was no clear evidence of any persistent variation in form, such ns occurs 
by the Poet's Seat in Greenfield, or on the back of the First Mountain, 
south of Patorson, N. J. The entire mountain soQms to be a single 
heavy trap sheet, several hundred feet thick. When nearly at the 
bottom of the valley, between the main and the posterior range, an 
excellent series of exposures was found in a little gully leading down 
the slope. First there was a glaciated surface of firm trapi Descend- 
ing a little farther [ascending in the geological series), there was found 
some forty feet of ragged, rough surface, in part trap, and in part clearly 
a mixture of angular ti'ap fragments with sandstone. The surface of 
the trap is often vesicular, and in places shows included fragments of a 
denser kind. The sandstone is reddish, not nearly so hard as that found 
on the western face of Mount Tom, though harder than some of the soft 
fragments of trap, which weather out leaving a rough framework of 
sandstone ; at some points the bedding can be seen, but exposures are 

Along the mountain summit the texture 



generally too small and rusty for this. The trap fragments in the 
sandstone vary from small grains up to pieces one to three inches in 
diameter; some are dense, some Yesicular. This locality is about one 
fourth of a mile north of a strong gap in the posterior ridge, and is 
marked by a five-foot boulder of light granite. Crossing the marshy 
stream, a small outcrop of ordinary normal sandstone is seen on the 
opposite slope ; similar outcrops are found one fourth of a mile farther 
northeast, higher up on the face of the posterior ridge ; and finally, just 
below its trap, several feet of well metamorphosed sandstone appear, 
gray in color and quartzitic in texture. The trap here shows nothing 
peculiar. Crossing over the ridge and descending a quarter of the way 
to the river, we leave the trap and come to numerous outcrops of con- 
glomeratic sandstone, darker in color than usual, and containing plen- 
tiful scraps of trap, many of them vesicular, and in size up to three 
inches. The first of these outcrops is not more than fifteen or twerjty 
feet over the trap ; many others appear at a greater distance, even on 
the railroad a little below Smith's Ferry Station. It was there that 
I first saw them in 1877, in company with Professor N. S. Shaler and 

Mr. J. S. Diller. 

The upper contact was not found among these outcrops, but it ia 
excellently shown in Delany's Quarry, on the railroad and river bank, 
not quite half-way from Smith's Ferry to Holyoke. (From the quarry 
to Holyoke Station is about an hour's tiresome walk along the hot, sandy 
track.) Here the rock is freshly worked, and the upper surface of the 
trap is well shown to be very amygdaloidal, uneven, and knobby, as a 
lava flow might be, and upon it lies the fine dull dark reddish muddy 
shale, fitting closely to the trap and filling up its inequalities, so that 
the sandstone a few feet higher is evenly bedded (see fig. 37). This 
contact shale is as soft as ordinary shale at a distance from the trap; it 
is easily scratched to powder with a knife. On some trap faces patches 
of similar shale appear to be included in the trap, but as they also are 
not metamorphosed, I consider them to be muddy fillings of cavities 
near the rough old lava surface, reached by passages not now exposed 
to view ; where their bedding shows, it is about parallel to that of the 
sandstone above. There was no appearance of branching intrusion into 
the sandstone, or of breaking across its layers. I looked carefully at a 
great number of freshly exposed amygdules here and elsewhere, in hopes 
of finding some of them banded like those at Brighton, Mass. (see Bos- 
ton Soc. Nat. Hist. Proc, XX., 1880, 426), but was always unsuccessful. 
Ten or fifteen feet of sandstone over the trap are well shown in the 

' J 



quarry. Several layers contain distinct fragments of trap, rather an- 
gular in form, and variable in structure from dense to vesicular. These 
layers are darker than the normal red sandstone, some being nearly 
black, presumably on account of the trap sand they contain; some 
might be mistaken for metamorphosed sandstone, as they have faint 
bedding, and in a rough way resemble trap ; but they grade into normal 
reddish sandstone below as well as above, and this clearly shows that 
their color is not due to metamorphic action. There is a strongly slick- 
ensidcd joint at right angles to tho dip in this (piarry, with some evi- 
dence of a fault of several feet throw. 

Hitchcock wrote (e, 442) that a tufaceous conglomerate "reposes on 
the greenstone on the east side of Mounts Tom and Holyoke ; and con- 
sists of a mixture of angular and rounded masses of trap and sandstone, 

with a cement of the same materials I do not doubt but the same 

rock may be found on the east side of nearly all the greenstone ranges 
in the Connecticut Valley. Its thickness is but small, and it graduates 
on one side into greenstone, and on the other into sandstone." This 
evidently refers to ,a bed similar to those above described, and points to 
the same conclusion. He refers to it again in the Ichnology {h, 17). 
Lyell (a, 794) visited this region in his company, and concluded "that 
there were eruptions of trap accompanied by upheaval and partial denu- 
dation, during the deposition of the red sandstone." Da:.a quoted Hitch- 
cock's results in 1863, and added, "But after an examination of the 
region the author regards it more probable that the appearance of scoria 
is owing to an escape of steam laterally from between the opened strata 
during tho ejection of the trap of the adjoining mountain," {b, 430.) 
Emerson's observations, made recently (196), confirm Hitchcock's and 
those of the present writer. In his last edition of the Manual (1880), 
Dana makes no mention of overflows. 

C. West Sprmgfieldj Mass. (fig. 38). — About two miles west of this 
station on the Boston and Albany Railroad, the track passes through a 
short cut in the second posterior trap ridge near its end on the north 
bank of the Wcstfield Eiver, and fortunately reveals some twenty feet 
of sandstone below the trap, as may be seen even from a passing train. 
The natural outcrops in this neighborhood are very poor, as the ridge is 
almost smothered in the high sand plain of the Connecticut River. The 
main ridge and the first posterior are also very poorly shown as far as 
critical outcrops arc concerned, though the trap itself is well opened in 
the city quarry by the railroad on the west face of the main ridge, where 
distinct columnar structure is apparent. In the railroad cut, it is 

i 1 



noticeable that the hardness of the lower sandstone 'docs not depend 
entirely on its distance from the trap, but rather on its composition. 
A sandstone stratum, some twenty-five feet below the contact, is red 
and very hard ; then comes some softer red shales ; above these some 
soft gray shales, and finally, next to the trap, several feet of hard red 
sandstone. The strata strike N. 25° E. ; dip 20^ E. S. E. The two 
rocks here are very firmly welded together at their junction ; the line 
is slightly irregular, but its average conforms precisely with the bed- 
ding. Within a foot of the contact, the sandstone is somewhat vesic- 
ular ; within an inch, its color changes to light gray, and in texture it 
becomes a firm dense quartzite. The adjoining trap is dark and dense, 
and but slightly amygdaloidal. The rest of the cut is all in trap, but 
the rock is by no means of uniform structure. There is first a mass 
from twenty-five to thirty feet thick (at right angles to dip), of which 
the greater part is ordinary dense trap ; but its upper six to eight feet 
become very amygdaloidal and loose-textured, and the upper limiting 
line, clearly seen on both, sides of the cut, dips closely parallel to the 
sandstone strata ; near the bottom of the cut it exhibits some irregu- 
larity. Over this, but separated by an open seam, comes a second mass 
of dense trap, of about the same thickness as the first. This is not so 
decidedly amygdaloidal as the first in its upper part, and is limited 
above by a very even six-inch band of coarsely crystalline trap, dis- 
tinctly visible on both sides of the^cut. Ten feet higher, there is an- 
other coarsely crystalline band, four inches thick, then say eight feet 
of massive trap overlaid by drift ; no upper sandstone could be found. 
These even persistent bands dip parallel to the sandstone; they are 
rather abruptly interpolated in the trap, and the whole is firmly welded 
together. I do not feel satisfied with any suggestion yet presented in 
explanation of them ; but there can be little doubt that the lower mass 
with its amygdaloidal cover is a single lava flow, buried under later 
eruptions. One can hardly imagine a clearer example of the kind. A 
number of small faults-can be seen on the sides of the cut, well marked 
by a foot or. so of brecciated trap ; the fault planes are all at right angles 
to the dip of the ^sandstone; the largest throw was only a foot, with 

uplift on the east. 

I have been unable to connect trie ridges here with the single poste- 
rior range by Mount Tom, and cannot say how they arc related to one 


D. Becldey, Conn. (fig. 39). — The several curved ridges shown on 

Percival's map (1, 2, 3, north end of E. III.) in the towns of Berlin and 


\ _ 


» * 



I I 

WethcrBficld, give clear explanation of the two causes that have produced 
the crcsccntic outlines so characteristic of the trap. The first (1) is 
shown to be a flat fold, a faint canoe-synclinal outcropping to the north 
and west, by the close parallelism of the sandstone ledges around its 
front ; their strike changes so as to run parallel to the trap bluff, and 
they dip towards and under it on three sides. The trap shows a steep 
face on the convex, and a long gentle slope on the concave side of its 
crescent. It is undoubtedly a thin overflow sheet; for although no 
contacts were scon, nonnul red sandstone was found three feet below 
the trap, and red shaly sandstone fifteen feet above it, on a cross-road a 
quarter of a mile southwest of Beckley Station ; and the trap is compact 
at the bottom, and very loose and amygdaloidal on top. Evidently, 
then, the sandstones and the trap have been here slightly folded to- 
getlier, and erosion has revealed their canoe-form precisely as it has 
brought out the greater canoes of Medina Sandstone in Pennsylvania. 
The eastern side of the canoe is not visible except at its northern end, 
or bow as it may be called, because the fold is canted over on the east. 
The fold as a whole has a gentle eastward dip. 

The second curve (2) is made of trap much like that of the first, and 
it is very probably the same trap sheet brought to the surface again by 
a north and south fault with upthrow of forty or fifty feet on the east; 
its curve docs not seem to depend on a fold, but simply on the cross 
valley of the Mattabesio ; for a stream cutting through a monoclinah 
ridge always produces such a retreat in the outcrop line of its deter- 
mining hard stratum. The second and third crescents are therefore to 
be regarded as parts of a single fold, cut into the imitation of a double 
fold by the stream between them. 

It becomes, therefore, an important matter to determine which of the 
crescentio ridges shown in Percival's and other maps are due to folding 
of the trap sheets, and which to erosion withoxit folding; E. I. and 
E. 11. are undoubtedly folds; so is the great curve of E. IV. that runs 
up into Massachusetts. New Jersey shows several others. But the 


peculiar forms of E. IV. 1, 2, 3, are chiefly, if not entirely, duo to erosion, 
as is shown under the next heading. 

Percival gives a close description of the facts about Beckley (358), 
but makes no statement of their cause, 

E. Meriden, Conn. (figs. 40 ~ 43). — Two days' walking about the 
Hanging Hills and Lamentation Mountain failed to discover any con- 
tacts, very probably on account of keeping mostly to the roads so as 
to cover more ground, for the work here was chiefly stratigraphical. 

1 1 


■ I 



The main result found was that the Hanging Hills and the neighbor- 
ing trap masses marked on Percival's Map, E. IV. 1, 2, 3, 4, 5, and 
probably 6, and others farther north, are all parts of a single trap sheet 
of overflow origin, broadly and faintly folded into a very flat synclinal, 
perhaps a little faulted, and deeply cut by erosion around the margin. 
It is pretty surely an overflow, because it has small influence on the 
sandstone when the two are seen near together, and its upper part is 
very amygdaloidal ; and because it makes part of the Mount Tom 
range, whose overflow origin is well established. The former union of 
the now separate hills is made sufficiently sure by the nearly uniform 
height of the hills on the opposite sides of a gap (see section, %. 41); 
by the uniform slope in a single plane of the separated parts of the 
sheet (fig. 40) ; by the conformity of this slope to the dip of the 
adjoining sandstone, wherever seen ; and by the regular position of 
the first anterior ridge on the slope below the great bluffs. This is 
not apparent from Percival's description or map ; on the latter, his 
outlines indicate only the ridges or elevations, not the areas of trap. 
Professor Dana's reduced copy of this part of the map {c, 418) unites 
the hills as here drawn, but he regards their trap as an intruded sheet 
{dy 41). West Peak (E. IV. 3), the highest of the Hanging Hills, owes 
its height over 2 and 4 to being at the southwestern end of the flat 
synchnal ; to the same structure is due the change in the direction of 
the blufls at this high point from a north and south to an east and west 
line. E. IV. 5 is higher than 4 chiefly because it is farther from the 
axis of the synclinal ; it is noteworthy that the oblique gaps between 
3 and 4, 4 and 5, etc., are about parallel to this synclinal axis, and may 
very probably indicate the position of subordinate bends or breaks. 

I believe it probable and provable that Lamentation Mountain (E. 
III. 5) is a reappearance by faulting of the Hanging Hills overflow sheet, 
and it may extend even through E. Ill, II, and I, as is explained below 
under faults and folds. 

F. Wallingford^ Conn, (fig. 45). — The sandstone in this neighbor- 

hood is loose and coarse, with wclhmarked cross-bedding; it is cut by 
many dikes, as was first stated by Chapin in 1835, but there are also 
several sheets nearly conformable to the bedding. The dikes are well 
seen on the road to Cheshire, half a mile or more southwest of the 
Wallingford Station (New Haven and Hartford Eailroad), where they 
break through the sandstone very irregularly : they are from five to 
twenty feet thick, but do not affect the adjoining sandstone for more 
than a few inches. Fig. 45 shows the ragged edge of lone of them. 





Besides the dikes, there are sheets of trap cutting the sandstone at 
a small angle, or perhaps in places conformable to the bedding. One 
of these begins close to the corner of the Middle Turnpike and the 
Cheshire road, and can be easily followed several hundred feet obliquely 
up the slope to the northwest; it makes a little bench on the hillside, 
rendered clearer by some quarrying work at several points ; it is about 
fifteen feet thick, dense throughout, and its columns are closely at 
right angles to its bounding surfaces; the sandstone is baked for a few 
inches below it, and the only sandstone found on its back was hard- 
ened. Another similar bench is seen a little higher; and a third makes 
a well-formed mesa near by, locally known as Mount Tom. All of these 
are probably ijitrusions ; but they have not the regular vertical position 
shown in Chapin's general section (see fig. 8). The trap here is more 
Irregularly intruded than at any other i)laco I have visited. 

There is a good exposure of sandstone on 

The strata here 

G. N'ew Haven, Conn. 

the southwestern face of West Rock imder the trap, 
are of coarse granitic sand, and red and purple shales; sometimes firm, 
but with several purple shaly beds; they do not show so much mcta- 
morphism as the rpcks beneath the Talisades, but nevertheless appear 
to be distinctly changed from their original condition for several feet 
from the trap, thus gaining a compact crystalline texture in certain 



The trap is fine at the base, where it is conformable to the 

sandstone, and very compact through the whole mass : no amygdaloid 
was seen at any point on the face or back. 

The eastern slope near the southern end of the Rock is covered by 
shaly sandstone, for a considerable distance toward the top ; it is often 
exposed in little gullies, and shows a variety of colors from gray to 
purple and bright brick-red. But for several hundred foct beyond the 
uppermost exposure, no rock is seen till the firm trap appears ; at least 
such is the case on the path leading up to the "Judges' Cave,"* and 
along several gullies farther south. Undoubtedly a junction may be 
found by searching farther to the north. In the covered space, several 
fragments were found resembling baked shale; they are probably from 

nearer the junction. 

Pine and Mill Rocks are simply large dikes of compact trap, about 

vertical, cutting across nearly horizontal granitic sandstones ; a marked 
consolidation has been produced by their heat for ten or twelve feet at 
least from their sides. Their width and direction are variable : the 

* A rude shelter under some boulders, where ** Cromwell's Judges" were con- 
cealed for a time. 







former is certainly as much as two hundred feet at some points ; and 
their general trend is east. A rough but distinct columnar structure 
is seen at right angles to the sides. Their junction with the sandstone 
is somewhat irregular; but this is natural, as the latter has no well- 
marked joint plapes. 

East Rock shows two patches of lower sandstone on its southwestern 
face ; they are very similar to that described under "West Rock, except 
that about eight feet below the conformable junction, a spotted appear- 
ance has been produced in a layer of purplish granitic sandstone. The 
trap is also like that of West Rock. Ascending by the road on the 
southern side of the hill, and when the eastern slope is reached turning 
across a field into the wood, a very strongly baked granitic sandstone 
is found within a few feet of the fine compact trap : the sandstone is 
very dense and much more cn^^stalline than any found elsewhere iu 
the Connecticut valley, but it rapidly loses this character, and becomes 
soft and fragile farther down the hill, like that found on the back of 
West Rock. 


A number of dikes (fig. 44) may be found by crossing the river from 
New Haven by Tomlinson Bridge, and continuing half a mile along 
Forbes Avenue toward East Haven. These were long ago described by 
Hitchcock (bj 56), but his figure (here copied, fig. 2) makes them much 
too regular; they vary in strike and, dip as well as in thickness, and 
their sides are uneven. They are not at all amygdaloidal ; their bak- 
ing extends one or two feet into the adjoining granitoid sandstone. 
The second cut on the Shore Line Railroad east of Fair Haven shows a 
similar dike ; but the third cut is in a coarse granitic sandstone that 
makes a strong ridge by itself, being hard enough to stand up between 
the softer shaly sandstones on cither side, though not visibly aided by 
any igneous rock. The ridge west of Saltonstall's Lake (Pcrcival's 
E. I.) is cut at a low gap by the same railroad, and shaly sandstones 
are exposed, conformably covered by trap, and baked to white quartzite 
immediately at the junction, as at West Springfield. The lino of con- 
tact is broken at one point by a very small fault, displacing the shales 
and trap equally, and evidently of later date than the eruption. The 
trap is brecciated at certain points, and is generally uneven in its joint- 
ing, and its upper surface along the lake shore is very amygdaloidal. 
No overlying sandstone could be found. 

There is fairly good evidence that the natural gap, cut deeper by the 
railroad, results from a transverse fault of ten or twenty feet, with the 
throw eastward on the southern side. 






Reference to Percival's description of these ridges is given farther on. 
Professor Dana gives a brief mention of the traps of this district {d, 46 ; 
most of this article applies to the quatcrnarj features of New Haven). 
E. S. Dana and Hawes describe the composition of the trap here and 
elsewhere, and note an increase in the hydration and alteration of the 
eastern traps over the western. (See below, under Composition of 
Trap.) All of the trap is regarded as intrusive by these authors. 

From the descriptions given above, and a comparison of this region 
with otlicrs, I am led to believe that the Saltonstall Ridge is an over- 
flow : its small metamorphic effect at the base, its decided amygdaloidal 
texture on the back or upper surface, its irregular and brecciated 
structure, and its -alteration and hydration, all agree with the characters 
of overflow sheets rather than with those of well proven intrusions, such 

as East Rock and the Palisades. 

Palisade Range. — H. Fort Lee and Englewood, N. J, — Sandstone 
shows at the water's edge above and below the wharf at Fort Lee. 
About eighty feet up the hill, under the Bluff Point House, a path cut- 
ting shows baked shales seven feet from the trap * A two-mile walk 
northward from hej-e leads one obliquely over the range toward Engle- 
wood, showing many wclhglaciated knobs of coarse, dense trap on the 
way ; the glacial stri£e advance obliquely up the back of the range, bear- 
ing S. 20^^ E. 

Floraville, a mile south of Euglewood on the Triassic Map of New Jersey 
(Cook, a), gives a good exposure of the iq)pcr contact of sandstone on 


The trap is of rather coarse texture when first shown in the stream ; 

it is evenly divided by parallel joints, one to three feet apart, dipping 

12° W. N. W., just as the sandstone dips farther on; the columnar 

structure is subordinate to this appearance of bedding. Followmg down 

the stream-bed, the texture soon becomes finer, but is nowhere vesicular, 

and in a short distance highly metamorphosed sandstones and shales are 

reached. Their bedding is very even, and not perceptibly disturbed 

near the trap ; their color varies from nearly black to gray or greenish ; 

in texture they are jaspery or distinctly crystalline. The junction was 

* Contacts could certainly be found by further searclung. The bluffs at Shady 
Side Landing, a few miles down the river, and under Englewood Hotel, two miles up 
stream, scorned worth visiting, as seen from a passing boat. Mather (282) gives 
examples of contacts farther north ; some of his figures are here copied (figs. 11-14). 

t *0ook mentions sandstones overlying the trap at Englewood (&, 178, 208). I was 
directed to Mill Brook, as a stream likely to show the desired contact, by Mr. J. II. 
Scrviss, of Englewood, 

A small stream known as Mill Brook, shown close to 






found with difficulty, and only after passing over it many times, up and 
down stream. It was at last discovered in a block, slightly moved from 
its original position by frosting and stream-work, but still preserving its 
joint faces parallel to those in the ledges near by. The ledge from 
which this block had been loosened was covered; but as trap in place 
was found two feet below it, and baked sandstone in place three feet 
above it, I have no doubt that it showed the true place of junction. Its 
weathered face showed no change of color, and very little change in tex- 
ture, and specimens showing the actual welded contact were found only 
after much hammering. They closely resemble those found at the 
"Weehawken tunnel at the under contact ; in both cases the igneous rock 
is bluish black, dense, and fine, and for a quarter of an inch from tho 
contact is chilled to a dark gray ; and the aqueous rock is gray or dark, 
and the more distinctly crystalline of the two. The thickness of the 
Palisade Eange trap between these contacts is, according to a true scale 
section by Cook (&, 200), about seven hundred feet. Some twenty feet 
of metamorphosed beds are seen farther down the brook ; then expos- 
ures are rare. A hard reddish-white sandstone was found farther south 
lying say one hundred and fifty feet over the trap. No posterior ranges 
of trap are known in this district, unless the Snake Hills back of Hoboken 
are so called. 

This excursion can easily be made in an afternoon from New York ; 
going up the Hudson to Eort Lee by boat from Canal Street, and re- 
turning from Walton Station, Northern Railroad of New Jersey, to the 
Erie terminus. It is of value, as upper contacts are rare. 

J, Weehawlcen, N, J. (fig. 46). — The several exposures of the sand- 
stones below the trap in this district have been fully described by 
Bussell {d)\ some of his figiires are here copied (figs. 30, 31), and a 
more detailed view of the junction at the point of rocks below the 
Duel Ground* is added (fig. 46). H. Credner examined the Palisade 
trap in 1865, and pronounced it intrusive; he regarded the Snake Hills 
as a branch from the main '* emporbrechende Dioritmassc" (393). 

It is very probable that the advance of the Weehawken cliffs to the 
river bank at this point is due in part to the resistance to erosion offered 
by the chimney or dike of trap, which here descends close to the water's 
edge, while elsewhere the trap generally rests on a sandstone base, thirty 
to one hundred feet above the river ; but it is also quite possible that a 
fault, similar to that seen at Garret Rock, Paterson (L), has aided tho 
advance. The intersection of the sandy and shaly layers by the dense 

* The Hamilton -Burr duel ground of ISO-l. 


• « 



trap, and their metamorphism, are excellently shown. The branch diko 
cannot be traced quite to the greater mass, but they undoubtedly join 
below the talus; tho^ branch is about four feet thick, generally lying 
evenly between the layers, but at one point crossing them in an irregu- 
lar, ragged passage ; it is clearly traced two hundred feet horizontally ; 
and where it is lost to sight the main trap mass of the high cliffs above 
has risen nearly half this distance over it. All the bedded rocks here 
are thoroughly baked, and near the junctions are more or less clearly 
crystallized ; their color varies from light gray to black, but there arc 
no red beds ; the beds above the branch dike are affected quite as 

stongly as those below it. 

Half a mile farther north, where the tunnel of the West Shore road 
(New York, Lake Ontario, and Western Railroad) opens on Day's Point, 
another contact was found. Here the fine dense trap lay evenly on the 
baked and crystallized layers below it, of which some eight feet were 
shown ; their color was dark or black, not red. This contact will prob- 
ably bo covered by later work. Day's Point, a low triangular projection 
into the Hudson, where the wharves of the West Shore Eadroad are in 
process of construction, now shows a small ledge of sandstone, rapidly 
being cut away in the work of grading. It is separated from the" trap 
by eighty or one hundred feet of sandstone, measured at right angles to 
the dip of 12°. The upper layers of the ledge are firm, fine-grained, and 
red ; the lower are looser, clear white, with some coarser grains of trans- 
parent quartz. Similar white sandstone occurs under the cliffs a third 
of a mile southwest of the Duel Ground. 

K. Jersey City, N. J. — The recent work of straightening the old cut 
on the Pennsylvania Railroad gives an excellent section with many fresh 
exposures through this lower part of the Palisade Range. The trap ia 
generally coarse ; in some small patches there were crystals of pyroxene 
half to three quarters of an inch in length. It was nowhere found to be 
the least vesicular. Broad joint faces are very common, and faulting 
has taken place on some of them. Near the eastern end of the cut 
there is a vein or dike, six inches wide, vertical, trending about north 
and south, in the trap. It is light gray in color and is composed of a 

fine granitoid mixture. 

Its texture is uniform throughout, and the 

I have found no 

trap shows no change of structure on approaching it. 

other example of the kind. 

Both Cook {h, 216) and Russell (i, 43) give evidence to show the 
existence of a soft bed, probably of sandstone, between the eastern and 
western part of the trap. Its place in the cut is marked by an open hollow 



in which no rock is now to be seen, and it is not fully proven not to be 
a fault like that at Garret Rock, Paterson. There is a longitudinal 
valley on top of the Palisade Range at Fort Lee, but coarse trap is seen 
so plentifully on its two slopes that there is little room for sandstone at 
the bottom ; and its cause is very probably a fault. Cook also notes 
that the trap of the Palisades is remarkably uniform and^ very hard 
(6, 178), 

L. Paterson aiid Little Falls, N. J, (figs. 47, 48). — First and Second 
Mountains* are here cut through by the Passaic. The flat country 
back of the broad gap and the considerable quantity of drift in the 
neighborhood indicate that the present course of the river is not its 
course during prcglacial times of greater land elevation. We cannot, 
therefore, now see the old valley bottoms, so that here, as on most of 
the Palisade Range, the back of the trap is stripped of its sandHtone 
cover below the present general surface of the valley drift, and upper 
contacts cannot be found. In spite of the deep river gorges, and the 
large areas of trap exposurCj I was unable, in searching a day and a half 
in this district, to find any sandstone lying on the trap; but lower con- 
tacts are seen at several points. The best of these is in the gorge below 
the Passaic Falls at Paterson: on the left bank the exposure is in a 
high biiiff, not easily reached; on the right the trap is quarried for pav- 
ing-blocks, and a fresh contact constantly shown and easily accessible 
(fig. 48). 

There are red strata of firm sandstone and thin-bedded shale cut 
below the trap, and up to a few feet of the junction they show no marks 
of alteration ; both can be matched closely at many points distant from 
any igneous rock. Within a foot of the contact the sandstone becomes 

F ' 

firmer than usual, and shows rusty cavities, presumably a metamorphic 
effect, as they are most numerous by the trap. The upper half-inch of 
sandstone is darker than the rest but still reddish. The line of junction 
is easily found and traced ; it is parallel to the sandstone layers, and 
nowhere cuts across them ; the slight waving irregularity that it shows 
does not demand intrusion for its explanation. Specimens are easily 
broken out showing the two rocks welded together. The mass o.f the 
trap in the gorge is dark, fine, and even in texture; farther back from 
the sandstone it becomes coarser, but no samples were found so coarse 

-8 those from the Jersey City cut or from Goat Hill on the Delaware. 

Illose to the junction, amygdaloidal cavities are very plenty ; but most 
of them are within a foot or even half a foot of it, and hero the trap is 

Called the "Watchung Mountains in Cook's later Reports, 








very fine-grained. The lower ten or fifteen feet of trap is of very heavy 
columns, two to four feet on a side, irregular or roughly rectangular- 
divided near the middle by rather continuous joints parallel to the sand- 
stone bedding, sometimes breaking the rock into slabs two to ten inches 
thick. No change of texture is seen at these joints, and some of the 
columns are continued above and below. The heavy columns suddenly 
change vipwards to smaller ones, six inches to a foot on a side, but there 
is no corresponding change in the texture of the rock, nor is there any 
appearance of a seam between the two parts; it is simply a change of 
jointing, for which I can suggest no satisfactory cause. The smaller 
columns are not all parallel, but incline in various directions; some 
variation is shown in the figure whore they overhang the lower columns. 
Where thus irregular in position, they are at right angles to the present 
surfiice of the ground (noted also by Cook, h, 202, 203). The same 
change of structure is shown a third of a mile south, by Barber's Mills ; 
again a little farther where the Delaware, Lackawanna, and Western 
Railroad cuts a bench for its passage around the end of First Mountain, 
here known as Garret Rock; and finally in the first and third of three 
quarries opened on the eastern face of the mountain, over the railroad 
station. Contacts of trap and sandstone show in all but the first of 
these, but not so clearly as at the Tails; the sandstone shows no eftect 
of heat except the sliglit one above described. Of these latter localities 
the most important is that on the railroad (fig. 47), showing two strike 
faults of small throw. The eastern and greater of the two is covered by 
a ravine and its rubbish, but is proved by the repetition of shaly sand- 
stone, heavy coltunns, and smaller columns on either side ; from junction 
to junction measured along the track is one hundred and sixty paces, 
say four hundred and fifty feet; the junction line dips with tiie bedding 
10°; this gives seventy or eighty feet for the displacement, with down- 
throw on the east. The Second fault, a little farther west in the same 
cut, is shown to be about eight feet by the displacement of the upper 
surface of the heavy columns with downthrow to west; the fault is on 
an open joint, parallel to the columns, and striking with the ridge. 

The mountain is most easily ascended by its northwest flank ; from 
any of its higher knobs* a welhmarked longitudinal valley is seen sep- 
arating the eastern from the western summits; it extends several miles 
with varying distinctness, and is very marked at the Notch, where the 

* Most of these knobs are well rounded by glacial action, and some still retain 
strire pointing directly np hill. Excellent scratches on the trap at Little Falls point- 
up into Vernon Valley between the two mountains. 

VOL. VII. —NO. 9. 18 



The right bank 

Greenwood Lake Railroad crosses the mountain. As the valley is in 
line with the larger fault, they probably stand in the relation of effect 
and cause ; the throw has very probably increased where the valley is 

well formed. 

Sandstone was not found in the valley as far south as the Notch, 
although the j)lace is favorable for its preservation. If continued north- 
ward, the fault would pass east of the trap front at the Falls, and its 
effect, if existing thci'C in the sandstone, woidd be less noticeable. 

On the western foot of First Mountain two small exposures just west 
of the Morris Canal and south of the High Bridge showed amygdaloidal 
trap, and one of them presented clear marks of variation in structure 
bounded by curved surfaces, such as are found farther south at Fclt- 
ville. There was also seen at this point a surface much like that of 

flowing lava or slag. 

Sandstone is not seen in the flat valley until the village of Little Falls 
is reached, a short mile west of the First Mountain trap, where it is 
shown in normal condition in a quarry by the canal and river, about 
two hundred yards east of the Second Mountain trap, 
of the Passaic here approached gives no chance of finding a junction ; 
but on the other side, a little farther down than opposite the quarry, 
there is a small opening in which fine trap and red sandstone both show, 
though the contact, is hidden by several feet of rubbish. The sand- 
stone has no marks of baking. Following up stream, the trap varies 
greatly in texture ; an irregxdar very amygdaloidal mass grades into 
firm trap on one side, and into a much decomposed loose rock on the 
other; I have considered the latter an ash or tuff. The dense trap is 
often distinctly columnar, and above the canal bridge it is well divided 
by nearly horizontal open joints into sheets of varying thickness. In 
the midst of this there is a very uneven mass of amygdaloidal trap that 
seems to contain fragments. Farther west there is a broad area of flat 

alluvial meadow-land. 

The trap of this region is described by Rogers (c, 146) and Cook 

. (6, 179). 

M. Feltville, N, J. (figs. 49, 50). — Mr. I. C. Russell {a) describes an 
npper contact in a little ravine on the back of First Mountain near this 
deserted village; but I failed to discover any outcrops corresponding 
closely to his description. My time there was shoi^t, and allowed only 
the examination of a ravine about an eighth of a mile east-northeast of 
the village ; the stream from it enters the brook in Washington Valley 
at the lower part of an old broken dam. Going about one hundred yards 




from the mouth, so as to descend (geologically) below the trap surface, 
the rock appears firm and hard in the stream bed : slialj sandstone 
often outcrops on the banks of the ravine, but at no point within five 
feet of the trap, and generally ten or fifteen feet from it. Eeturning 
down stream, the trap becomes amygdaloidul, and shows rounded 
bosses or knobs similar to those described by Eussell; but as seen here 
they are not directly at the upper surface of the trap. Nearly at the 
entrance of the ravine, a bank of much-weathered vesicular and frag- 
mental trap suggests a trap breccia, but the surface is too much rusted 
for determination. The most important exposure licrc was found in the 
side of a short adit made some years ago on a small vein in the trap ; it 
is known in the district as the "Copper Mine." It shows (fig. 49) a 
number of oval masses of trap, up to two feet or more in diameter, con- 
tained in a peculiar red and black matrix. The trap masses vary iu 
their texture and color with the distance from their surface; the outer 
part is black and dense, then amygdaloidal for a few inches with con- 
centric bands of color, and rather dense near the centre. The matrix 
(fig. 50 a, b) has all the appearance of being a disorderly mixture of 
small, angular scraps of trap, up to an inch long, held in a soft reddish 
shaly mass, that shows no signs whatever of metamorphism. Its con- 
trast with the over-lying sandstones at Englcwood is very marked, and 
it is diflicult to understand how this could have been formed except on 
the surface of a pre-existent sheet of lava. 

Russell says (a, 280), ''The section at Feltviilc furnishes indisputable 
evidence that the igneous rocks composing the first Newark Mountain 
were intruded in a molten state between the layers of the stratified 
rocks subsequent to their consolidation." He describes (6) another 
upper surface of the trap on the back of the same mountain farther 
south, back of Plainficld, where there is "an amygdaloidal trap passin 
into a metamorphosed shale," so tliat it is frequently difiicult to detect the 
difierence between the two rooks. I was unable to visit this point. 

Feltville can bo reached by a pleasant walk of four miles from Fan- 
wood Station, Central Hailroad of New Jersey ; the Triassic Map of New 
Jersey, 18G7, gives the roads very clearly. It is to be hoped that further 
observations will soon be made to give evidence for one or the other of 
the above discordant conclusions. At Fanwood Station, the railroad 
cuts the unstratified terminal moraine of the quaternary ice sheet (New 
Jersey Geol. Survey, Annual Reports, 1877, 10; 1878, 10); and good 
specimens of foreign angular and scratched stones, large and small, are 
easily found. 




N. Martin's Dock, K J. (fig- 51). — Two beds of trap appear in the 
shales a little above Martin's Dock on the north (left) bank of the 
Raritan Eiver about two miles below New Brunswick; they are there- 
fore about three miles posterior to Pahsades — Eocky Hill trap range, 
which if continuous is here buried under the cretaceous formation. The 
lower bed is about iifteen feet, the upper two feet thick, and they are 
separated by some ten inches of slate ; the two are closely parallel to 
each other and to the strata of shale and sandstone below and above, 
and all dip ten to twelve degrees westerly ] there is no appearance 
whatever of the traps cutting across the shaly layers that cncluso then). 
The section may be described as follows, beginniug at the bottom. 

Soft, fragile shales, generally red in color, appear along the shore for 
several hundred feet down stream : occasionally they vary to a fine, 
sandy layer, six to twelve inches thick, with rather irregular layers, as 
if disturbed, although the shalo below and above is very evenly bedded. 
Approachiug the traj^, three to five feet below it, the shale is grayish, 
but still soft and fissile; for six or eight inches below the trap, the shale 
becomes slaty, dark, tending to bluish black, and hard ; but in places 
two or three inches under the junction occur loose, soft, weathered 
patches quite unlike the firm, dark shale enclosing them. The trap 
and shale are not welded together ; all the junctions are separated by 
open joints, so that no specimen showing the two rocks together could 
be obtained. The lower heavy trap layer is firm, dense, dark through- 
out with finer texture at both junctions, and no appearance of vesicular 
structure ; it breaks into rough colunmar blocks, and where these are 
weathered on the shore, they often have the ragged look of a breccia, 
but no such structure could be found in the rock in place. The inter- 
mediate stratum is a hard black ringing slate : in places it shows a 
slight breaking and disarrangement of its layers, not by cross-faulting or 
any general disturbance, but more as if kneaded together. The upper 
trap layer is dark and dense, like the lower. Above it the rock is very 
rusty from weathering, and shows an open, loose texture for some six 
inches; the rusty color continues for several feet, and about ten feet 
from the trap there are normal soi't red shales again. 

These trap-sheets must be intrusive, although they show less baking 
than similar sheets on the Delaware. Cook says (6, 202), speakiug of 
the bedded appearance of the trap here and elsewhere, '' So strongly 
marked are these divisional planes, and so closely do they resemble 
marks of stratification and even lamination, that good observers are 
frequently unable to tell which is trap and which is only discolored 










shale." He includes this with the general occurrences of intrusive 

0. Point Pleasant Station, Belvidere Railroad^ N. J. (fig. 52). — The 
main mass of trap here seems to be a small example of what is shown 
on a larger scale farther down the Delaware about Lambertville, but 
the smaller sheets resemble most the little outcrops at Martin's Dock, 
and are finely shown. 

The first outcrops on the railroad are about five hundred feet below 
the station^ where a dark, fine grained trap shows in the bank ; it is 
fliintly columnar, but clearly bed-jointed, so that the slabs dip 12° N. 
20^ W. ; the sandstone wherever seen is closely of the same position. 
There are no amygdules, but on some weathered surfaces the trap is 
pitted in lines parallel to the bed-joints, sho\^^ing points of cliemical 
weakness probably determined early in its history. The rock rapidly 
becomes coarse-grained and light-colored on going northward, and in 
this form rises to the hill-top ; on the slope wlicro seen, it is not colum- 
nar, but breaks out in large masses and slabs; it becomes somewhat 
finer again, but I failed to find its northern limit, which occurs in a 
ravine. North a little farther and opposite the station is a bed of fine- 
grained dark trap, again showing distinct bed-joints and little cavities 
weathered in lines parallel to its lower surface ; there is no apparent 
change of structure to cause them. This trap rests on a fine, brittle 
bkick slate ; the junction of the two rocks is seen with few interruptions 
for a hundred feet, and is precisely conformable to the bedding. The 
upper surfiice of tlie trap was not seen ; but judging by the form of the 
bank, the bed is not more than twenty feet thick. 

A little above the station there is a clifi', thirty to fifty feet high, of 
fine black trap ; its face is marked by joints a little steeper than a nor- 
mal to the dip, and dividing the rock into sharp-edged columns (o) ; 
there are other joints parallel to the bedding of the adjacent sandstone; 
and two four-Inch bands of the same dip were traced some forty feet 
along the face, distinguished from the rest by a peculiar roughness of 
weathered surface dependent upon short cracks occupied by calcitc. 
This may be called a kind of vesicular structure, but not at all like the 
ordinary trap amygdaloid. No contacts of this trap with slates were 
seen, but tlic slate wlicre found above and below was fine, black, and 
brittle, and dipped 12° parallel to the bed-joints in the trap. 

An eighth of a mile above the station, a dry stream bed gives a 
good scries of exposures to a height of more than two hundred feet over 
tlie river. Much the greater part is on fine black shale or slate, or 






brownish shale of somewhat coarser texture ; near the several trap 
sheets, it is always black and brittle. Mud-cracks were noticed on 
many loose slabs, and occasionally in place here and farther up the 
river. Four beds of fine black trap occur in this little ravine : the first 
two form a -single shelf over which a fine thread of water falls (fig. 52), 
the lower bed being four feet thick, the upper twelve, with four to 

six inches of shaly slate between them. Ihis parting of slate is seen 
between the two beds of trap, extending with uniform dip for seventy 
feet. The slate and trap are very much alike on fresh surfaces, but the 
slate has a bluish tinge, and shows some signs of breaking on its bed- 
ding ; the trap is blacker, and its fracture is more conchoidal. Both 
arc jointed into sharp-edged cohuxms, but these are most distinct in the 
trap. Farther from the trap, the shaly structure is more apparent, 
and bands of lighter and darker color arc sometimes found. The other 
two trap sheets make two small benches farther up the ravine, and 
show about the same characters as those just given, but their junctions 
with the slate could not be determined, so nearly alike were the tex- 
tures of the two rocks near their contact, and so closely did joints in 
the trap imitate beds in the slate. Weathered fragments of trap often 
showed a pitted or scoriaceous surface, though no cause could be seen 
for this in the structure. 

Ecturning to the railroad, and going north again, the same trap 
sheets are passed as they descend to cross the river. A quarter of a 
mile above the station, dark red sandstone appears in the bank, and 
continues without further interruption; it is fine and hard, though not 
at all quartzitic ; generally thick-bedded, but sometimes shaly and mud- 
cracked ; fine green dots of epidote (^) are found in it. It is very 
evident that the brittle black slate that adjoins the trap was never like 

this sandstone. 

Rogers (c, 156) and Cook (b, 192) both refer briefly to this locality. 
The trap here is shown on the Triassic Map of 1867, but not on the 
Economic Map of 1881 (Cook, a and d). 

■ P. Lamhertville, N. J. — The section along the Delaware by Lam- 
bcrtville is spoken of by H. D. Eogers (c, 153; g, 685) as affording 
good examples of the metamorphic effect of the trap on the sandstone 
on both sides of the igneous mass. Cook shows the same region in a 
generalized section (a, sec. 1, here copied, fig. 26), with the traps \ymg 
between the sandstones after the manner of sheets elsewhere. The 
region is one of difficult study, for, in spite of the deep valley cut by 
the Delaware, outcrops are not continuous enough to show junctions 3 






« w 



it seems hopeless to look for them here, and I was unable to get good 
evidence as to the position of the trap. It is surely intrusive, as no 
amygdaloid is present, and the shales are baked on both sides of the 
trap ridges ; but whether interbedded or in dike form, is rather an 
open question. Against the sheet form may be noted the small dif- 
ference in slope of the two sides of Sovudand Mountain, and conse- 
quently the absence of a well-marked face and back so characteristic 
of the sheets elsewhere; and the fact that the baked and blackened 
shale ascends to about the same height on either slope (Cook, 6, 191). 
Farther southeast, the several elevations known as Rocky Hill, Penning- 
ton Mountain, and Bald Pate arc on the other hand probably sliccts, 
as their soutliern face is steeper than the northern : as suggested by 
Eussell, these are presumably the reappearance of the Palisade curve, 
which is covered by the cretaceous strata in its middle ; its length from 
Ilavorstraw on the Hudson to Bald Pate on the Delaware would then 
be over eighty miles. 


The following paragraphs show in brief the opinions of various writers 
on this subject, the districts of their observations, and the dates of their 

It was thought that the trap was intrusive by Silliman (Conn., 1810, 
1830), Hitchcock (Mass., Conn., 1818), Chapin (Conn., 1835), Gesner 
(Nova Scotia, 1846), Lyell (Va., 1847), Emmons (N, Y., 1846, N. C, 
1858), Cook (N. J., 1868), E. S. Dana and Ilawcs (Conn., 1874), Kerr 
(N. C, 1875), Prime (Pa., 1875), and Frazcr (Pa., 1876). These authors 
make no special reference to the effect of the eruptions on the position 
of the sandstone strata in their writings of the above dates. It was 
held that the intrusion of the trap tilted the sandstones by A. Smith 
(Conn., 1832), Percival (Conn., 1842), Emmons (1854), and in part by 
Silliman Jr. (Conn., 1842) and Hitchcock (Mass., 1844). 

The following considered the trap intrusive, but held that the dip of 
the sandstone was due to some other disturbing force : Jackson ana 
Alger (Nova Scotia, 1833), H. D. Rogers, (N. J., 1836), Hitclicock in 
part (Mass., 1844), Credner (N. J., 1865), J. D. Dana (Conn., 1863- 
1880), Heinrich (Va., 1878), and Russell (N. J., 1875-1880). 

The overflow origin of the trap was faintly suggested by Gibson (Pa., 
1820) and Cooper (N. J., 1822) ; it was shown to be probable by 
Hitchcoct in 1833, and proved later (Mass., 1841-1358); Dawson came 



to the same conclusion (Nova Scotia, 1848-18G8) ; it was adopted by 
Ljcll in part (iVTass., 1842), and fully by Loconte (1878) and Walling 
(Mass., 1878). These authors agreed with those of the preceding group 
in believing that the tilting of the sandstones was the effect of some 

external force. 

The trap was considered passively intrusive, and the dip of the sand- 
stone was looked on as the result of original oblique deposition, by H. D. 
Rogers (Pa., N. J., 1839), W. B. Rogers (Va., 1840), Mather (N. Y., 
1843), Silliman Jr. (Conn., 1844), and Whelpley (Conn., 1845). 

The former anticlinal connection of the two sandstone strips in North 
Carohna was suggested by Kerr in 1874, and extended by Bradley in 
1876 to the Connecticut and New Jersey areas. Russell independently 
made the same suggestion for the latter in 1878. 

The trap has been considered a metamorphosed sedimentary deposit 
by Wurtz and Martin (N. J., N. Y., 1870). 

Plate I. may be taken as a pictorial supplement, in illustration of 
the preceding abstracts. It embraces nearly all the sections that have 
been drawn showing the Triassic traps within their sandstones. These 
drawings are not fac-similes, but in the small changes that have been 
made I think no injustice has been done. 

1. Hitchcock {a). Across the Connecticut Valley in Northern Mas- 
sachusetts. The vertical position of the greenstone intersecting the 
strata of Deerficld Mountain was corrected in his next article (/>), but 
in the mean time it had served Cooper as an argument for the igneous 

origin of floctz-trap. 

2. Hitchcock {h). East Haven (Conn.) dikes; their sides are too 

regular and parallel. See our figure 44. 

3. Eaton (c). Across the Connecticut Valley in Northern Massachu- 
setts ; excessively wrong. 

4. Smith. Across the Connecticut Valley; sandstone tilted by the 
trap, which rose through chasms and overflowed at the surface. 

■ 5. Jackson and Alger {h). Southeastern side of Bay' of Fundy. 

6. Hitchcock (c, 221). Across the Connecticut Valley in Nortlicrn 


7. Id. (c, 423). Turner's Falls on the Connecticut in Northern Mas- 
sachusetts. The increased thickness of the main trap sheet at the sur- 
face is wrong. 

8. Chapin (105). Across a number of ridges at Wallingford in 
Southern Connecticut. The author failed to observe any interbedded 






9, 10. Chapin (109, 111). Details in the same region. 
11, 12. Mather (PL V., figs. 5 and 4). Dikes iu the sandstone under 
the Palisade trap, two miles south of Havcrstraw, and near Vcrdrictje 


13, 14. Mather (PI. XLY., figs. 3 and 2). Sections across Southern 

New York and Northern New Jersey, 

15. H. D. Kogcrs (c). Across the Newark Mountains, Central New- 
Jersey. The intcrbcdded position of the trap is not shown. 

16. Emmons (6, 200; c, 107). Palisade section at Slaughter's Land- 
ing, showing intrusions between the beds below the main mass of trap. 

17. Lyell (c, 271). Dike in the Richmond Coal Field. 

18. Dawson (a, PL V.). North shore of Mines Basir., opposite Two 
Islands, Nova Scotia. Part of this section gives the appearance of a 
post-Triassic overflow, but it is all described as contemporaneous. 

19. Lesley (a, 133). Hypothetical section illustrating the use of 
" overflow " by Pogcrs as well as by the author. 

20. Hitchcock {(j, PL HI.) Mount Tom, Mass., with incorrect in- 
crease in thickness of the trap sheet as in fig. 7. 

21. 22. H. D. Rogers {g, IL 912, G91), Dikes at New Hope and 
Gettysburg, Pa., producing motamorphism and cleavage. 

23. Id. (</, Gcol. Map l\i., sec. 8). General section near Gettysburg, 
Pa., showing post-Triassic eruptions. 

24. Emmons (d, sec. 1). Dike in North Carolina, 

25. Cook (b, 200). True scale section of the Palisades. The author 
says this *' fails to impress the mind" as one of the exaggerated sections 
does ; but it certainly has the advantage of giving a true impression. 

26. Cook (rt, sec. 1), East bank of Delaware by Lambertville, N. J. 
There is some doubt as to ■whether these trap masses are sheets as hei'e 

27. Frazer (a, 298, sec. 11a). Dikes near Gettysburg, Pa. It is 
not definitely stated in the context -whether faults exist as shown in 
this section. 

28. Leconte (440, 441). Hypothetical section of the Connecticut 
Valley. If drawn on true scale the amount of erosion would bo still 
more enormous. 

29. Russell (c, 230). Hypothetical section of the New Jersey and 
Connecticut Triassic belts, showing their supposed anticlinal relation. 

30. Id. {d, 47). Section of the Palisade trap at Wechawken, N. J. 

31. Id. ((/, 42). Ideal section of intrusive trap sheet. The descend- 
ing branches seem to be of improbable occurrence. 






Origin of the Triassic Estuaries. — The small number of Triassic 
trough-deposits and their absence from the western half of our Eastern 
mountains go to show that in the making of the Appalachians the svn- 


;linals were not, as a rule, absolutely depressed, but on the contrary 
took part in the general elevation, and rose with the rest of the strata, 
although to a less height than the anticiinals : as they were continually 
rising above drainage level, they very seldom or never served as troughs 
for the accumulation of deposits. But, on the other hand, the estuaries 
or troughs in which the Triassic strata were deposited must have been 
absolutely depressed below their previous levels; and it seems reason- 
able to suppose that the remarkable relation existing between the trap 
and sandstone areas, so often alluded to, must be mechanically depend- 
ent on this downfolding or absolute depression of the estuaries; for 
here alone where there is evidence of absolute local depression are the 
only post-carboniferous eruptions of trap to be found from the Green 
Mountains to Alabama. That this may be truly a relation of cause 
and effect is made the more probable by the evidence given in the fol- 
lowing pages that much of the trap, if not all, was ejected during the 
downfolding and filling in of the troughs. 

Professor Dana (e, 113) considers that the subsidence which ended in 
the post-Triassic eruptions was slow, and not more than five thousand 
feet, and that it caused in the end only small disidacements of strata, 
wholly inadequate to cause the fusion and ejection of deep-lying rocks 
from which the traps were derived. He further instances the Green 
Mountains as a region where the folding was much stronger, and yet 
where no eruptions but only mctamorphism took place, and takes this 
as arguing against the possibility that the moderate Triassic disturbance 
was the cause of the fusion and ejection of the traps. 

However it may bo with the fusion, I must differ from this opinion 
concerning the eruptions; it seems best, in view of what has been stated 
above, to suppose that the Triassic disturbance was directly and can- 
sally connected with the fact and act of the eruptions. The occurrence 
of absolute depression in the slightly disturbed Triassic troughs seems 
reason enough for mechanical eruptions taking place here, althougl 

absent elsewhere in regions of greater disturbance but general absolute 


* 4 



Origin and Deposition of the Triassic Strata. — There seems to be no 
sufficient reason to look upon these stratified deposits as very abnormal 
in their origin. Their material was derived from the highlands adjoin- 
ing either side of their estuaries of lakes of deposit, and whatever the 
agent of importation — glaciers, streams, waves, or tides — the layers 
were probably coarser along the shores, finer in mid-water, and all essen- 
tially horizontal when deposited. It is noteworthy that those who look 
on the present dip as the result of original oblique deposition took this 
ground less from direct evidence in favor of anything so extraordinary, 
tlian from the hope of escaping from what seemed a greater difficulty ; 
namely, the tilting to a (supposed) constant dip in one direction in each 

monoclinal belt. 

In addition to the great improbability of the theory of oblique depo- 
sition, and its mechanical difficulties of one sort and another, it haa 
to explain why very nearly all the detritus should have been derived 
from only one side of each estuary ; and this in the fixce of the frequent 
occurrence of licavy conglomerates of local derivation on the other 
side. With the coarse material in the conglomerates, there must have 
been introduced a groat quantity of finer detritus, which was carried 
farther from shore : how could this have, been deposited dipping so uni- 
formly towards its origin 1 The general absence of conglomerates along 
the outcrop sides of the estuaries, appealed to by Kussell (c, 231-238, 
251) as evidence of open water and not of shore line there, is partly and 
perhaps sufficiently explained by the fact that the outcrop side must 
have lost a large share of its original mass on account of its elevatiou 
and erosion. But it should be remembered that conglomerates or coarse 
sandstones of local origin do occur on the outcrop sides of the belts. 
Such are mentioned by Percival (430), Cook (&, 336; c, 31, 34), H. D. 
Eogcrs (g, 6G0, 677, 679, 760), and Kerr {h, 141). An example of peb- 
bles found on one side of a Triassic belt and derived from the other, 
is given by Wurtz (100) : he describes fragments in the sandstone 
beneath the Palisades coming from Green Pond Mountain, which stands 
northwest of the Triassic area. Further detailed study on the position 
and source of these conglomerates is much needed in order finally to 


prove or disprove the theories ab»ve mentioned. 

The conditions and order of origin of the various strata, 
erate, sandstone, shale, limestone, and coal,' — their even, cross-bedded, 
and ripple marked structure, and the causes that brought about a change 
from one to another in this series, cannot be determined with any defi- 
niteness until the strata are better co-ordinated than they are at present. 





I believe that in Connecticut and elsewhere there are repeated outcrops 
of the same beds, produced by faults as described below ; but their iden- 
tification is now a difficult matter. Microscopic analysis and detailed 
Btudy by local ob.'^ervcrs will do much to solve this diificulty. 

Composition of the Trap. — The composition of the eruptive rocks In 
the Triassio belts is not discussed here, as the present work relates to 
their physical characters. For this reason, the general term trap is em- 
ployed throughout. Many names have been previously used, — whin, 
greenstone, trap, basalt, sienitio basalt, diorite, trachyte, dolerite, and 
diabase ; but the last two would seem the more proper ones, judging by 
mineralogical composition. Chemical analyses and microscopic exami- 
nations of the trap from various localities have been made by Cook, 
E, S. Dana, Frazer, Hawes, Schweitzer, and Wurtz. The following 
statement gives the limiting percentages of their results : — 

Silica 45.8-53.4% 



Alumina 12.5 

Iron oxides . 


Magnesia, Lime, Soda, Potash, less than 10% each. 

The minerals present are pyi'oxene, labradorite, and magnetite, with 
certain accessory species, and chlorite as a common product of alteration. 
E. S. Dana (391) and Hawes (a, 185) note an increase in hydratation 
and alteration in going eastward across the Connecticut. It is notice- 
able that the least modified traps are dikes or intruded sheets, and the 
most modified are overflows, according to the present determinations ; 
thus Hawes describes East and West Rocks and the Jersey City traps 
as dolerites, and the Saltonstall and Durham Mountains (Conn.) as 
diabases : Mount Holyoke gives an exception to this apparent rule, as 
it is classed under the dolerites, although it is certainly an overflow. 
The two authors above named considered all the trap as intrusive, and 
consequently did not perceive the natural relationship between condi- 
tions of origin and composition, as here suggested. 

Relations of the Trap and Sandstone. — Two views as to the ori^.n )f 
the trap sheets have been discussed. According to one, they are con- 
sidered eruptive across or between the sandstone layers, and more or 
less active in aiding the breaking, tilting, consolidating, and coloring of 
the strata, after the period of deposition had ceased. The other view 
looks on the trap sheets as younger than the sandstones below, and 
older than those above them; or, as it maybe stated, the sandstones 
and traps are geologically contemporaneous ; the sheets are old lava 
overflows buried under strata of later date than their eruption. 




The following review, arranged by localities, beginning in the noi-th- 
east, will give an idea of the various opinions that have been held. 

In 1833, Jackson and Alger (6, 276) described the Nova Scotia trap 
along the Bay of Fundy as "an immense dike, thrown up from beneath 
the sandstone through some vast and continuous rent, produced by the 
sudden eruptive upheaving of its strata, which allowed it to spread out 
laterally only to a very limited extent." In 1846, Gesner included the 
same traps under the heading " Intrusive Igneous Eocks." 

In 1848, Principal Dawson in describing these sheets said (58) that 
volcanic action ''brought to thQ surface great quantities of melted rock, 
without disturbing or altering the soft arenaceous beds through which 
it has been poured, and whose surface it has overflowed." This is quoted 

in his Acadian Geology, 1868. 

Bailey and Matthew mention stratified columnar and vesicular traps 
and trap conglomerates on Grand Manan ; but further speak of the 
traps as intrusive (219, 220). 

For Massachusetts, Hitchcock's first section (1818) shows the trap as 
a vertical dike breaking across the sandstones; this was soon changed 
(1823) and the trap and sandstone were described as in alternate beds 
(6, 48), separating the old red sandstone on the west from the coal for- 
mation on the east. In 1833, he described the conglomerate on the 
back of Mounts Tom and Holyoke, consisting of "angular and rounded 
masses of trap and sandstone, with a cement of the same materials," 
and concluded that some of the trap must have occurred as a con- 
temporaneous overflow {d, 211). In 1844, the same conglomerate is 
ascribed to small precursory outbursts during the formation of the sand- 
stone ; but the larger ridges are considered intrusive and of later date. 
In 1858, he decides that all the Massachusetts trap is of overflow origin, 
as will be referred to below. 

Lyell was shown the trap conglomerate on the back of Mount Tom 
by Hitchcock, and inferred " that there were eruptions of trap, accom- 
panied by upheaval and partial denudation, during the deposition of the 
red sandstone" (a, 794). Leconte and Walling both adopt Hitchcock's 
final view, and it is recently confirmed by Emerson. 

The rocks in Connecticut have given rise to other opinions. The 
elder Silliman held that the trap was eruptive, but did not reach the 
surface (1810-1830) ; his observations were mostly made when it was 
still discussed whether the trap might not be of aqueous origin. Cooper 
took strong ground in favor of the igneous origin of the trap, but did 
not concern himself with the manner of its eruption : he implies, how- 



ever, a belief in overflows (240), though he quotes no decisive observa- 
tion in this direction. Smith considered the trap eruptive over the 
tilted layers of the secondary strata (225, 227), andChapia represented 
all the ridges about Wallingford as vertical dikes (fig. 8). 

Percival states that the traps "have obviously the character of intru- 


sive rocks of igneous origin," which exerted " apparently a controlling 
influence" in determining the arrangement of the sandstone (10, 11). 
The trap occurs in dikes and ridges ; the dikes are small ; the ridges 
are steep on one side, and on the other are frequently overlaid by sand- 
stone, "thus apparently forming interstratified masses or inclined dikes." 
"In some instances, where the middle portion of a ridge appears thus 
interposed, or merely as an overlying mass, its extremities appear as 
distinct vertical dikes." 

n n 

Ihe ridge and the dike may thus be regarded 
only as modifications of the same arrangement." (300.) His use of the 
term "volcanic" (as 311) docs not seem to imply that the eruptive 
rocks ever reached the surface: nor docs " cotemporary formation" 
(299, 321) seem by the context to indicate the contemporaneous origin 
of the traps as used in this article. He would apparently agree with 
those who considered the trap eruptive after the making of the sand- 
stone, often appearing between its layers and strongly affecting its 
position. The younger Silliman at first (1842) thought the sandstones 
tilted by the intrusion of the trap, but later reported to the American 
association of geologists, in 1844, that the sandstone had been deposited 
as now standing, and that the trap had been intruded without disturbance 
and had seldom reached the surface. Whelpley held similar opinions. 

Professor Dana (h, 430) refers to Hitchcock's observations on the 
back of Mount Tom, and adds, "But after an examination of the region, 
the author regards it as more probable that the appearance of scoria is 
owing to an escape of steam laterally from between the opened strata 
during the ejection of the trap of the adjoining mountain." In the later 
editions of his Manual, he makes no mention of overflows. He states 
that the trap " has come up through fissures in the sandstone which 
varied from a few inches to three hundred feet or more in breadth. In 
many cases, it has made its way out by opening the layers of sandstone, 
and in such cases it stands with a bold front, facing in the direction 
toward which it thus ascended." (c, 419; also d^ 46.) "The manner 
in which the trap at its eruption has sometimes separated the layers of 
sandstone, and in this way escaped to the surface, instead of coming up 
through the fissures simply, shows that the rock had been tilted exten- 
sively before the ejection." (c, 421.) 




Akerly did not decide between the igneous or aqueous origin of the 
trap of the Palisades (62). 

For New Jersey, H. D. Rogers wrote in 1836 that the molten trap 
had burst up through nearly parallel fissures, after the sandstone had 
been tilted : the eruption caused no further change in the position of 
the strata, but produced certain changes in their contents and structure 
(a, IGO): and in 1840, "the protrusion of the trap, the formation and 
deposition of the conglomerate, and the elevation and final drainage of 
the whole red sandstone basin, have hardly been consecutive phenomena, 
so nearly sinudtancous appear to have been these changes." ((?, 171.) 
Cook considers the trap sheets intrusive, {b, 176, 200, 337; c, 32, 34.) 
Husscll gives good evidence of the intrusive nature of the Palisade sheet 
(d), and claims to have proved the same origin for the First Newark 
Mountain (a). Wurtz regards the Palisade sheet as nactamorphosed in 
place from sediments ; he is doubtful if this origin apply to the Newark 
Mountain as well (101). 

Pennsylvania gives so few good opportunities for observation, that 
little has been written about its trap sheets and dikes, though they ai-e 
extensive and numerous. Many are omitted from the State Geological 
Map, 1858. Farther south, dikes seem much commoner than sheets; 
and so far as I. have learned, there have boon only two suggestions of 
contemporaneous overflow for any of the trap southwest of New Jersey. 
The lirst, by J. 13. Gibson, was written in 1820 and published in 1825 : 
*' That the trap may have been deposited on the sandstone by a volcano 
before the present continent was elevated above the level of the sea, 
would bo a more plausible supposition ; but it would be altogether gra- 
tuitous." (Observations on the Trap Rocks of the Connewago Hills, 
159.) The second was by H. D. Rogers, who wrote : "In certain cases 
the entire length of each middle secondary bolt seems not to have been 
uplifted to the sea level before the commencement of the trappcan erup- 
tions; and those tracts which remained thus submerged are seen to con- 
tain, interstratilied, as it were, with the later sedimentary deposits, those 
sandy volcanic tuffs or subaqueous sedimentary forms of trappcan matter 
which constitute the link between the exclusively aqueous and igneous 
masses.'* (g, II. 762.) The context shows that such cases were regarded 
as very exceptional in Pennsylvania at least : no definite localities are 
given. "Overflow," as used by H. D. and W. B. Rogers (g, 11. 670 ; 6, 82) 
and Lesley (a, 133), seems to refer to eruptions after some erosion of 
the Triassic strata, so that the trap should lie unconformably on the 
sandstones : they all seem to regard the trap as post-Triassic, with slight 







Heinrich accepts the general view of post-Triassic intrusion for the 
Virginia traps (251). Fontaine writes that the " outpour " of fused rock 
occurred near the end of the period of deposit (29); but his attention is 
given more especially to the stratified rocks. Farther south than Vir- 
ginia, there is no mention of anything but dikes in the sandstone. 

It would thus seem that the overflow theory of the origin of the 
trap sheets has found its most pronounced supporters north of Con- 

There is theoretically no difficulty in distinguishing between the in- 
trusive and overflow modes of origin, and the practical difficulty and 
difference of opinion above shown are probably to be explained by the 
rarity of good points of observation. 

If the traps are intrusive, the sandstone above and below should show 
about equal signs of metamorphism ; there might be fragments of sand- 
stone in the trap, and such should be well baked, but there could be no 
fragments of trap in the sandstone; the trap might break across the 
sandstone layers, or send branches off from its main body ; the upper 
surface of the trap should not be scoriaceous, especially in the thin 
layers, for if intrusive it must have been under almost as much pressure 
as the lower surface. 

Examples of intrusive sheets elsewhere are described by the following 
authors : — ■ 

G. K. Gilbert. Geology of the Henry Mountains (Utah), 1877. The 
intrusive rock is not vesicular at all ; no fragments from it occur in 
the overlying strata ; metamorphism is marked as well above as below 
the intrusions. The name of laccolite was proposed by Gilbert for such 
masses of eruptive rock, and it may be applied to the Triassic intrusions 
as well. The laccolites of the West still retain their original horizontal 
position : those of the East have been tilted since intrusion. 

Other less detailed mentions of intruded sheets may be found in the 
Annual Reports of the Geological Survey of the Territories, 1873, 18G 
(Marvine), 234(Pea]c); 1874, 04 (Holmes), 219 (Endlich); 1875, 60, 
95 (Pealc), 268 (Holmes); 1876, 194 (Holmes): in the Bulletin of the 
same Survey, III. 1877, 551-564 (Peale). 

A. Geikic. On the Tertiary Volcanic Eocks of the British Isles. 
GcoL Soc. Journ., XXVIL, 1871, 270-310. The flows and intrusions of 
the island of Eigg are described in detail : the overflows have frequently 
been regarded as intrusions (292), but the two are easily separated 
by the difference in their metamorphic effects, and by the presence or 
absence of slaggy, amygdaloidal structure (281); the intrusions "are 

* * 



almost wholly confined to tho lower portion of tho volcanic series" 

A. Geikie. On the Carboniferous Volcanic Rocks of the Basin of the 
Firth of Forth. Edinb. Eoy. Soc. Trans., XXIX,, 1879, 437-518. 
Both intrusions and overflows are again recognized ; in the former, a 
cellular or amygdaloidal texture is hardly to be observed, and never 
when they arc largely crystalline (475) ; in the latter, amygdaloids are 
common (481). 

If the trap sheets are old lava-overflows, there must of course be 
supply dikes, by which the sheets were fed, and these dikes must cut 
across and bake and be younger than all the strata they pass through, 
but their cross-section will probably be small compared to the area 
of the overflows ; the sheets will be rather closely conformable to 
the strata over which they flow, though, as might be expected, their 
creeping advance while yet molten may have produced some disturb- 
ance, and they may contain sandstone fragments ; only the previousl}' 
formed sandstone beneath them can be baked ; the upper and lower 
surface of the flow should difler as in modern lava flows, the upper being 
more vesicular and uneven than tlie lower; one flow may cover another; 
the compact lavas may be preceded or followed by tufaceous or frag- 
mentary deposits ; tho overlying sandstone must lie conformably on the 
uneven surface of the lava, adapting itself to all inequalities, and grad- 
ually filling them to an even surface; it may often contain volcanic sand 
or fragments of lava. 

Overflow sheets are much more common than intrusions ; the follow- 
ing references will lead to descriptions of some of the more notable. 

K. C. V. Lconhard. Die Basalt-Gebildo, 1832. This work serves 
well as a guide to the older European observations on eruptive rocks. 
Both overflow and intruded sheets are recognized; the former arc de- 
scribed as scoriaceous on the surface, while the latter are generally dense, 
because gas bubbles could not expand in their heavily compressed mass 
(I. 473) ; but in speaking of the baking in the adjoining strata (11. 230), 
the author does not clearly state the different effects of the two kinds 
of sheets. 

J. W. Dawson. On tho Lower Carboniferous Bocks, or Gypsiferous 
Formation of Nova Scotia. GcoL Soc. Journ., I., 1845, (29-31). Sev- 
eral beds of trap conformably interbeddcd with the adjoining strata; the 
trapes dense below, amygdaloidal above, and its fragments are found in 
an overlying conglomerate. (See also e, 316, and section, 125; h, 49.) 

J. S. Newberry. Pacific Railroad Reports, Vol. VI., 1857, ch. vi., vii., 

VOL. VII. — NO. 9. 19 


p I 


3 J 

r ^ 



the overflows of the Columbia basin. Geological Ecport of the Colorado 
River Exploring Expedition, 1861; many observations. 

G. P. Scrope. The Geology and Extinct Volcanoes of Central France, 

1858, U. 

Mcdlicott and Blanford. Geology of India, 1879, I. 299. Amjgda- 

loids are very common, especially in the upper part of the various flows. 

M. E, Wadsworth. Geology of the Iron and Copper Districts of Lake 
Superior. Bulletin Museum Comp. Zool. Cambridge, VII. , 1880, 109- 
113. The trap sheets are amygdaloidal at the upper surface : they 
were first shown to be overflows by Foster and Whitney, in 1850, but 
various opinions have since been expressed concerning them. 

In the Western Territories, lava overflows have been very common, 
and have covered vast extents of country. They are mentioned in 
nearly all the Western Survey Ileports, but their overflow origin is as 
a rule so evident that few special descriptions are given of the characters 
that serve our needs of comparison. The following may be referred to 
from among many others : King, 40th Parallel Survey, I. ch. vii. sec. v. 
Geol. Survey of the Territories, 1874, 172 (Pealo) ; 1875, 145 (Endlich). 
C. E. Button, Geology of the High Plateaus of Utah, 1880, eh. iii. 

The above means of distinction between intrusions and overflows are 
almost self-evident ; but they have seldom been definitely stated in con- 
nection with our Triassic traps, and have often been entirely overlooked. 
The earlier studies of the traps were made when the controversy between 
the Vulcanists and Neptunists was still unsettled; it was sufficient then 
to show that the traps were igneous, not aqueous. But later than this, 
and down even to recent dates, observations on the traps seldom give 
secure basis for statement of their mode of origin, for the essential and 
critical points for observation have been very generally neglected. In 
many cases the older observers gave no special attention to this physi- 
cal phase of ^the question ; their work being directed to some other of 
the many dilTicidtics that the Triassic rocks present; and hence from 
their accounts it is impossible to discover how the trap is related to the 
adjoining rocks. Even Percival's remarkably painstaking and accurate 
description of the Connecticut traps is often indeterminate as to their 
origin ; it is greatly to be regretted that he had not better opportunity 
to publish what he had learned, in addition to simple descriptions. 

The rare exposure of contact lines is extremely provoking : in the 
Connecticut valley alone their combined length must amount to many 
hundred miles, but so universal is the drift and talus covering, that one 
seldom finds more than a few feet of "junction'* exposed. And this 




13 especially the case for the more important upper contact with tho 
sandstone on the back of the trap ; for during the agea in which these 
rocks have been eroded, they undoubtedly stood frequently or always at 
a higher level above the sea than at present ; the soft beds were deeply 
worn away, aiid are now buried under thp ^lays and sands of post-glacial 
weathering or of glacial deposit. Upper contacts are everywhere rare. 
Lower contacts are not very uncommon in Massachusetts, Connecticut, 
and New Jersey; but nearly all contacts are hidden in Pennsylvania 
and fixrther south. The discovery and description of the junction of tho 
trap with sandstone above and below it afford excellent field for local 
observations in all the Triassic belts. 

The observations of the past summer, as detailed in the preceding 
pages, give examples of nearly all the points of evidence required to 

prove an intrusive or an overflow origin of the trap sheets. The locali- 
ties where the best evidence of overflow sheets was found ai-e : — Con- 
formable, unbaked sandstone on the trap, or fragments of trap in the 
overlying sandstone, at Turner*s Falls ; on the back of Moimt Tom and 


its posterior ridge ; and at Feltville, on the back of the First Newark 
Mountain. Tufa deposit with fragments or bombs of trap, under the 
second posterior ridge. Turner's Falls. A second lava-flow resting on 
the uneven amygdaloidal surface of an earher one, at West Springfield. 
Percival mentions a trap breccia or conglomerate at several points in 
Connecticut. Dawson represents a large mass of these fragmental trap 
deposits in his Nova Scotia section. 

Three distinct forms of occurrence must be admitted for these traps : 
first, the feeders, or supply dikes; second, the intruded sheets, generally- 
lying evenly between the enclosing layers; third, the overflow sheets. 
The second and third forms are generally closel)' alike in their present 
topographic features, and can be distinguished only by detailed observa- 
tion. Even in the best known districts, there is room for much work of 
this kind. 

Trap Dikes. — Under this heading will be included only those trap 
masses that have a greater extension across the sandstone layers than 
parallel to them. They have been observed as follows i 

Dawson and Harrington note a single occurrence of trap on Prince 
Edward Island in a dike form ; it is vesicular and scoriaccous in part, 
as well as dense and columnar (21). 

Bailey and Matthew mention a dike in the Triassic of Grand Manan 

Hitchcock says there are no well-characterized dikes in the Massa- 










chusetts Bandstones (e, G55) ; the only possible case of the kind was 
found on the south side of Mount Tom, near a saw^mill on a stream, not 
far from the main road three miles below Northampton (e, 05Q).'' 

In Connecticut dikes are comparatively common. The first examples 
recognized were described and figured by Hitchcock in 1823 (6, 56); 
they are in East Haven, eight narrow dikes within four hundred feet. 
(See figs. 2 and U.) Chapin was the first to describe and figure some 
of the numerous and irregular dikes about Wallingford in 1835 (fig. 10). 
Percival refers to all of these, and adds many others ; but it seems that 
he sometimes applied tlie word dike to sheets, and therefore we cannot 
say how many of his examples would come within our limitation. Pme 
and liill Hocks at New Haven (G) are the largest dikes observed in 

the State. 

Mather gives one or two examples from the face of the Palisades 

(279, 282, here copied, figs. 11, 12); 

Cook finds only two dikes in New Jersey ; one near Blackweli's Mills, 
on the east side of the Delaware and Raritan Canal ; the other in a road 
cut beyond the Flemington copper mine; but he tliinks it probable 
that many .others lie hidden below surface drift (6, 204; a). He later 
says there are many places where the trap can be seen cutting across 
the stratified rocks, as by Hook Mountain, Palisade range (c, 32). 

In Pennsylvania and beyond, dikes become more common. H: D. 
Rogers figures two examples (here copied, figs. 21, 22), and on the State 
map (1858) a number are represented within and without the sandstone 
belt : of the latter, the most remarkable is the long dike discovered by 
Henderson, which extends some eighteen miles, across the Juniata and 
Susquehanna near their junction. Frazer describes the dikes in Lan- 
caster and the adjoining counties as so numerous and so difiicult to trace 
that he was unable to represent them all on his map (c, 27) ; he says, 
also, *'The outflow of trap probably followed one or more of the planes 
of cleavage, of which these rocks are full'' (6, 325; his sections showing 
dikes are cautiously drawn without contact lines : compare extract below, 

' under Intruded Sheets). 

W, B. Rogers mentions dikes cutting across the sandstones in Vir- 
ginia (6, 82), and Heinrich writes that, "Penetrating the sedimentary 
rocks, igneous rocks are occasionally met with in the form of dikes" 
(244, also 250, 263). 

* Since writing the above, Professor C. H. Hitchcock tells me that he has seen 
one or two small vertical dikes cutthig the sandstone In a (luarry on the southwest 
slope of Mount Holyoke about half a mile from the Connecticut, - the only examples 
of the kind known to him in the State. 




Ljoll shows a dike in hia section of the Hichmoud coal field (c, 271 ; 

our figure 17). Olmsted (c, 236) and E. Mitchell speak of trap dikes 

in North Carolina. Emmons does not describe or figure any sheets, but 

shows several dikes on his sections {d ; our hgure 24). Kerr states 

that the sandstones arc everywhere intersected in various directions by 

dikes of trap; their thickness varies from a few yards to two or three 

rods, and their length occasionally reaches several miles : the sandstones 

and shales are usually blackened for several feet or yards on either side 

of the dikes {h, 146); the dikes are usually transverse to the stratifi- 
cation (a, 48). 

It would seem from this review that dikes are rare in Nova Scotia, 
in Massachusetts and Northern Connecticut, and in New Jersey; while 
they arc common in Southern Connecticut, in Pennsylvania, and farther 
south. They are of all sizes up to two hundred feet, Mill Hock and Pine 
Rock just north of New Haven being the largest well-known examples. 
They arc, as a rule, dense and compact, with a rough columnar structure 
at right angles to the sides; some are reported as amygdaloidal, but 
such are clearly exceptional ; their vesicles are very likely not of gas- 
bubble origin" The sides of the dikes are not smooth, like the sides of 
most of the dikes in the- old jointed slates about Boston, but are more 
or loss irregular or even ragged (fig. 4o) ; implying that there were no 
joints to guide their fissures. It should be noted, how vcr, that some 
of the looser sandstone is still almost without joints, and in such cases 
this point of evidence is of no value. Their metamorphic effects are not 
far reaching so far as observed : a dike ten feet wide bakes the sandstone 
for a foot; a hundred-foot dike has some effect t-fi or twelve feet away. 
None of these dikes have clearly the form of "necks" or "chimneys," 
such as are described by A. Geikie about the Eirth of Forth (Edinb. Boy. 
Soc. Trans., XXIX., 1879, 468). 

Intruded Trap Sheets. ~ k number of sheets named in the following 
list cannot be regarded as fully proven to be of intrusive origin : the evi- 
dence for Pennsylvania and the States farther south is very incomplete. 

There seem to bo no intruded sheets north of Middle Connecticut. 
Farther south, near New Haven, East and West Eocks (G) and the 
northern continuation of the latter have long been rightly regarded as 
intrusions. Smaller examples occur at Wallingford (F), and doubtless 
many more may be found. 

Percival's descriptions make it very probable that all his western lino 
of elevation from East and West Kocks at New Haven north to South- 
ington are intrusive traps. In evidence of this, we may note the general 







absence of amygdaloid here (tncntioncd once on 403), and the frequent 
mention of indurated sandstones above as well as below the trap. The 
sandstone near the trap by East Rock (W. S. I. 1) * " is remarkably in- 
durated to an unusual width" (395). Two points on the back of East 
Rock show *' highly indurated sandstone" bordering the trap (396), 
Mill Rock (W. S. I. 2) is a dike rather than a sheet, and is bordered by 
"light gray very indiirated coarse sandstone" (390). West Rock 
(W. S. I. 4) is overlaid or bordered on the east by indurated sandstone 
(399). The dikes or ridges of W. S. I. 7 arc bordered by "singularly 
altered and indurated" sandstone (401). Roaring Erook shows indu- 
rated sandstone on the back of W. S. 11. (403). "At different points, 
in connection with the western line of trap," dark purple, black, and 
bright indurated sandstones arc found (437). Professor Dana classes 
East and West Rock, Mount Carmcl, and the Mcriden Hills with the 
dikes of Pine and Mill Rock, as trap "that came up melted through 
wide fissures in the sandstones and subjacent rocks" {d, 46). 

The Palisades give the largest example of intrusion : this origin was 
6.rst well proven for them by Russell (d ; see also our observations, H, J) ; 
Emmons noted, a number of years ago, that branching intrusions oc- 
curred in the sandstones below {h, 200; his figure is here copied, 16). 
Smaller sheets are found in New Jersey at Martin's Dock (N), and on 
the Delaware (0) ; whether the large coarse trap masses by Lambert- 
ville (P) are dikes or sheets, I cannot fully decide ; but they are not 
overflows. Cook inclines to the intrusive origin of all of these (6, 17G, 
200); he mentions the occurrence of transverse dikes by Hook Moun- 
tain, the north end of the Palisade Range (c, 32), which would seem to 
correspond to the large dikes by West Rock, Conn. H. D. Rogers^s 
sections represent intruded sheets in the Pennsylvania sandstones near 
the surface (here copied, fig. 23); and Frazer says of the traps about 
Lancaster County, "As a general rule in this region, their dip corre- 
sponds to that of the beds between which they were poured out " (6, 318 ; 
compare with the quotation above, under Dikes)., 

W. B. Rogers describes the trap in Virginia as " not unfrcquently 
entering between the layers of sedimentary rock, or pouring out and 
overspreading them at the top" (6, 82) ; and Lyell writes of the trap 
in the Richmond coal field that it, " although intrusive, has often here, 
m is so common elsewhere, made its way between the strata like a con- 
formable deposit." But all these latter references are inconclusive as to 
intrusions or overflows; they leave the question open for further work. 


* The notation use J by Percival. 



The trap sheets which arc definitely determined to bo intrusive show 
no vesicular structure at any point so far as I have seen them ; they are 
dense throughout, fine at the margins and very coarse in the centre of 
the larger sheets. Their metamorphic effect on the adjoining sandstones 
is very inarlvcd, as will be described below. The even intrusion of those 
sheets between shaly or sandy strata is very remarkable. At Martin's 
Dock and Point Pleasant Station, N. J. (N, 0, figs. 51, 52), where this 
is best shown, trap sheets of various thicknesses, from two to twenty 
feet, are seen evenly interposed between the strata above and below 
them for fifty or more feet, without breaking across the layers at any 
point : in two cases the slaty partings between adjoining trap sheets 
are less than one foot thick, and yet are continuous for over fifty feet. 
From this it must be supposed that the molten trap was injected slowly, 
and that it acted as a liquid wedge, prying open a passage for itself along 
the planes of easiest breakage that could be found : where two sheets 


are close together, one was probably intruded after the other, Slill it 
is surprising that any rock could break so evenly as the TriassiSiStrata 
arc thus proved to have broken. 

It is not a little interesting to discover that the largest clearly intru- 
sive sheets, the West Eock range and the Palisades, are found on the 
outcrop side of their respective sandstone belts; they are 'near what 
would be the bottom of the sandstone scries if the entire formation had 
receive^ a single monoclinal tilting. The intrusions on the Delaware are 
also near the base of the formation, as is shown by the appearance of 
the Matinal limestone not far from them. ' The probable cause of this is 
suggested below. 

The date of these intrusions is indeterminate. It cannot be fully 
Bhown when they took place ; whether at about the time of the over- 
flows, that is, the latter half of the Triassic time, or whether their 
intrusion came later, when deposition was stopped by upheaval and dis- 
location ; but the latter is the more common view. 

Professor Dana has already been quoted as taking the position of the 
trap sheets as evidence tliat their intrusion came after the sandstones 
had been tilted extensively (c, 421). But the laccolitcs of the Henry 
Mountains, Utah, as described by Gilbert, and similar intrusive rocks in 
Colorado described by Pcale (referred to above) lie between horizontal 
strata ; it is thereferc not necessary that the sandstones should have 
been tilted in order that the trap might be forced in between its layers. 
Professor Dana further argues, from the fact that the trap columns on 
the face of the ridges are at right angles to the sandstone layers, that 






'* there was a tilting of the strata in progress, before the final breaking 
and ejections " (c, 421). This is also inconclusive; for the same relative 
position of columns and strata obtains in the sheets that overflowed 
on horizontal layers, the entire mass being tilted bodily afterwards. 
We must therefore differ from the conclusion that the eruptions of the 
trap were necessarily the " closing events of the sandstone period," or 
that they took place in "a succeeding epoch" (c, 421). The overflow 
sheets were certainly of earlier formation : the mtruded sheets may 
have been so as welL 

Kussell states that the outbursts of trap occurred after the sedimen- 
tary rocks had been consolidated and upheaved, and at the time when 
the post-Triassio elevation culminated. His evidence for this view is 
theoretical (c, 245, 251) and is seriously weakened by the occurrence of 
overflows. The generalized section that he gives for the Palisade sheet 
(df here copied, fig. 31) shows some down-branching dikes of proble- 
matic occurrence. Cook classes all the traps as eruptive after the depo- 
sition of the sandstones and shales (c, 32). 

The evidence which points to an early date for the eruption of the 
intruded sheets is, first, the ragged line of contact with the sandstones 
where they are broken across ; this, as has already been mentioned 
under the dikes, indicates an eruption before the making of joint planes, 
and consequently before the tilting; but it is not final or conclusive. 
Second, the occurrence of intrusions chiefly on the outcrop side of the 
sandstone belts, or, in other words, near the base of the formation ; the 
only cause that I can suggest for such a limitation of position is that 
these laccolitic intrusions could only form at a considerable depth, and 
under considerable pressure, and were therefore placed near the bottom 
of the sandstones before the latter were , tilted : if the intrusions had 
taken place after the tilting, they might break out at one point as well 
as another, and would not be likely to have so peculiar a restriction as 
that above noted. Third, the intruded sheets have the same crescentic 
form as the overflows; and this, as will be shown farther on, results 
from folding after the eruptions : while it is possible that the intrusions 
were guided into their curved line of outcrop by the gently folded strata, 
it seems more probable that all were folded together. 

Eut, as stated above, this question is at present indeterminate; the 
above suggestions may serve to counterbalance opinions on the other 
side of the question, but not to settle the matter. It remains with a 
number of other points, notably the monoclinal structure, open for 
further observation. 


4 4 




The force which caused the intrusion of these sheets can hardly have 
been the expausion of vapors and gases, which plays so important a 
part in modern volcanoes ; for evidence of such expansion (vesicular 
structure) is wanting. It was therefore more likely mechanical, and 
connected as already suggested with the downfolding of the troughs 
rather than with the subsequent elevation and tilting of the sandstones. 
So far as this holds good, it also points to a Triassic date for the intru- 
sions as well as for the overflows. 

Overflow Trap Sheets, — By far the greater number of trap sheets seem 

to be of overflow origin. The proof of this origin is more or less com- 
pletely established for the following examples. 

The high trap clifl's of the Bay of Fuudy are described by Dawson as 
overflows, but he gives no account of their upper contacts, and his sec- 
tion (hero copied, fig. 18) shows much more irregularity than any that 
I have found in Massachusetts and farther south. But amygdaloids 
are very common in Nova Scotia, and these seem limited to overflow 
sheets. On Grand Manan the trap and amygdaloidal beds conform to 
the adjoining sandstones (Bailey and Matthew, Verrill). The Couuocti- 
cut valley gives many examples. jb'arthest north is Deerfield Moun- 
tain, as recently described by Emerson and as represented in this 
paper (A) ; the long range beginning at Belchcrtown, Mass., including 
Mounts Tom (B) and Ilolyoke, and extending to the Hanging Hills (E) 
by Meridcn, Conn., has been fully shown to be an overflow in its north- 
ern part, and it can hardly be of other origin farther south. Its lateral 
ridges are probably all overflows as well. Hitchcock's observations 
applied to the posterior ridge on the back of Mount Tom, and should 
have left no doubt of its mode of formation. 

In Connecticut, much observation is still necessary to decide finally 
on the origin of the numerous ridges. The evidence that favors the 
intrusive origin of ail Percival's western lino of elevation has already 
been stated. Equally good evidence may bo found to show that all the 
large and most of the small sheets of the eastern lines of elevation are 
overflows. The frequent occurrence of indurated sandstones, and the 
general absence of amygdaloids, in the west, contrast strongly with the 
lack of evidence of distinct metamorphism, and the frequent mention of 
amygdaloids, and trap and amygdaloid conglomerates, in the east. Toket 
M^ountain (E. II.) is described as dense trap at the base, amygdaloidal 
at the top, and overlaid by friable red shale (Pereival, 338). Lamenta- 
tion Mountain (E. III. 5) has swells of amygdaloid on the back, overlaid 
by shale (352). The anterior range is separated from the main range 







The ridge anterior to Lamentation Mountain is 

of Newgate Mountain (E. IV. 2. 2) by a band of friable red shale 
(391). A part of A. 1, S. of E. II. shows a peculiar dark green trap con- 
glomerate, accompanied by beds or dikes of amygdaloid and fine-grained 
trap (341). A conglomerate east of Saltonatall Lake contains fragments 
of a fine-grained light green sub-amygdaloidal trap, similar to that in 
P. 1 of E. I. (324). 
partly composed of a peculiar trap conglomerate, or rather brecciatod 
amygdaloid, distinctly parallel or stratified in its arrangement (3G5). 
Many similar extracts might be noted. 

In New Jersey, I believe First Mountain to be proved an overflow by 
observations at Paterson and Feltvillo (L and M), although Eussell takes 
the other view. As early as 1822, Cooper wrote that "this mass of 
floetz trap is poured over the old red sandstone" (240), but it is doubt- 
ful whether he had considered the possibility of its intrusion. Second 
Mountain is probably also an overflow, as its sheet is very amygdaloidal 
and irregular in structure near the under surface at Little Falls, and 
its effect on the underlying sandstone is very slight j but its upper con- 
tact has not yet been described. Cook mentions pebbles of trap in the 
sandstone beneath the First Mountain (6, 337), but later says that no 
fragments of trap are found in any of the stratified beds (c, 34). 

There are no decisive observations of contact for the trap sheets of 
Pennsylvania and the States farther south. H. D. Eogers speaks indefi- 
nitely of "overflowed" trap (^, 670), of amygdaloid near the borders of 
certain of the larger dikes (^, 671), and of "sandy volcanic tuffs" and 
" trap shales " interstratified with the sandstones, mostly in Nova 
Scotia, some in Connecticut and the Middle States (g, 762). Lesley's 
general section (copied in fig. 1 9) shows " the original sea, the lava and its 
vent, the manner in which it lifted the new red layers at its outburst, 
so soon as it was near enough the surface to do so, and overflowed them 
above" (a, 133), but evidence to prove this sequence of events is wanting. 

Heinrich mentions that amygdaloids arc found in the Virginia traps 

The sheets which are proved by their appearance at the contacts to 
be overflows have the following characters : they produce very little 
metaraorphic effect on the underlying strata ; they often show some ve- 
sicular structure near the base, sometimes within the mass, and are 
always very amygdaloidal at the upper surface. It cannot be said that 
amygdaloids occur only in the overflow sheets, for they are reported in 
some dikes, and in rare instances in intrusions ; but the vesicular struc- 
ture is as frequent in the overflows as it is rare elsewhere. 

d A 



Percival noted that the amygdaloids arc generally found in the lateral 
portions of the trap ranges, and occasionally make a large part of the 
lateral ridges (315); Hitchcock wrote that amygdaloids occupy "the 
easterly [i. o. posterior or upper] part of the ridges wherever I have 
examined them" {e, 045) j and Eogcrs, that amygdaloids arc common 
" near the borders of certain of the larger dikes " (y, 671). 

The occurrence and position of the amygdaloid has been variously 

explained. Jackson and Alger {h, 2G5) thought this texture resulted 
from the combination of the trap with sandstone and shale. 


stated that the amygdaloid occurred " in immediate contact with the 
altered red shale, by the reaction of the trap upon which this umygda- 
loidal character has been accpiired " (</, 761, 763). Cook says that if 
the cooling of the traps had been ''rapid and not under much pressure, 
they would be more or less cellular" (6, 215). Professor Dana con- 
Biders all the original trap to have been equally anhydrous at its deep 
source, and to become vesicular by the expansion of steam formed 
wherever water was mot in the process of eruption (d, -107). E. S. 

Dana and Hawes accept this cause. 

Several of these explanations are undoubtedly true and possible, but 
they do not sliow why the overflows should always be amygdaloidal on 
the back, and why the intrusions should so generally be compact. It 
seems most probable that the vesicular texture was produced in these 
old traps as it is in modern lavas ; not so much by meeting water during 
their eruption, as on account of a decrease of pressure which allowed the 
occluded gases and vapors to separate from the surface of the overflowing 
molten mass (Dawson, d, 63 ; e, 87). The difference in the composition 
of the eastern and western traps found by E. S. Dana and Hawes in 
lower Connecticut has already been referred to as resulting naturally 
from the better chance the eastern traps have had for alteration. 

The area marked by some of the larger ranges is very considerable. 
The Mount Tom — Hanging Hills range has a front sixty-five miles long, 

and, judging by the curves at either end, its breadth must be six miles, 
giving an area of nearly four hundred square miles. ' If the several loops 
down as fiir as Saltonstall Lake all belong to the same sheet, broken by 
faults, as is suggested below, then the length and breadth would be 
much increased, and the area might be over seven hundred square miles. 
The Newark Mountains in New Jersey would in the same way have an 

area of above three hundred square miles. 

But it is not by any means proven that these sheets are the product 
of single eruptions. The heavy trap which forms Mount Tom (B) do- 




creases in thickness or disappears entirely in going south, and the range 
is continued for a time bj a varying number of smaller sheets. So at 
Turner's Falls (A), the southward ending of the first and second poste- 
rior ridges seems as well explained by the giving out of the trap at the 
edge of its flow-area, as by the faulting suggested by Emerson. At 
West Springfield (C), the composite structure of the second posterior 
trap is well shown. In New Jersey the irregularities in the columnar 
structure of the Newark Mountains at Paterson and Little Falls (L) may 
be perhaps explained by supposing each mountain to be the product of 
several consecutive flows. It seems, therefore, probable that the long 
trap ranges represent a period of volcanic activity, rather than a single 
violent outburst, preceded and followed by periods of shorter or less in- 
tense activity represented by the anterior and posterior ridges. This is 
shown in Connecticut far better than anywhere else, and is beautifully 
illustrated by Percivai's remarkable map. 

The importance of the overflow trap ranges as marking horizons iu 
the deposit of the sandstones will be referred to later. 

Ilfect of the Trap on the Sandstone.^ • — A metamorphic effect is gen- 
erally attributed to the trap, by which the sandstone iu its neighborhood 
has been indurated and changed in color to a greater or less extent. 
The most exaggerated form of this idea ascribed the general red color 
of the whole formation to the effects of trap heat (Hitchcock, d, 242 ; 
sec also Percival, 430, and Dana, c, 420) ; but as red sandstones are 
common in other regions far from any contemporaneous or subsequent 
igneous action, it is more probable that their color here as well as there 
is essentially due to conditions of weathering at the time of deposit. 
Whether the contemporaneous volcanic action in the Conncicticut valley 
aided the coloring of the sandstones or not, is difficult to say; for bright 
colored strata are found far from and near to the horizons of the vol- 
canic rocks. _ But, as a general rule, the baked strata near the trap 
are not so red as the unaltered layers farther away. Above and below 
the Palisade trap sheet (H), the rocks were black, gray, or dull reddish- 
, brown, but not strong- or bright red as is common elsewhere. Under 
Mount Tom (B), the sandstones near and at the contact were gray or 
dull greenish-gray. Along the Delaware (0, V), the layers nearest the 
trap sheets or masses were black or dark gray ; the red strata appeared 
only several hundred feet on one side or the other, so far as seen : these 

* T have not yot had time to examine closely the inineralogioal changes produced 
by the trap ; some of these, as shown by specimens collected during the past sum- 
mer, are very striking. 

* * 



H. D. Eogers 

last are the most extended effects of the trap that I found. In the West 
Springfield raih-oad cut (C), the baked saiidatonc for a quarter or half 
inch from the contact was almost white on fresh surfaces. 

The absence of red color in strata near a contact has been noted by 
several observers. Silliman described the sandstone close under the trap 
of Eocky Hill by Hartford as gray or white (e, 125). Pcrcival found 
that the sandstones near the trap were "sometimes discoloured greenish 
or brawn, and at other times their usual reddish color is apparently dis- 
charged, leaving them nearly white" (319, also 436): in a few cases 
they are black or red (437). Lycll found some of the shales turned 
white below the traps of the Richmond coal' field (c, 271). 
described the shales near the traps as dull brown or pm^ple {g^ 673, 
678). The change to black color as a consequence of baking is men- 
tioned by Cook (6, 20G, 212) and Kerr (6, 147). In view of these facts, 
it is impossible to consider the prevailing color of the New Ked Sand- 
stone in any way dependent on the action of the trap after the deposit 
of the sandstones. How much effect the contemporaneous eruptions may 
have had upon weathering and color, is an open question. 

In regard to the effect of the trap on the hardness of the sandstone 
the most excessive views were those of H. D. Rogers, who considered 
most of the good building sandstone in New Jersey hardened by baking 
(c, 157) ; and of Whelpley, who thought that the sandstones had covered 
a broad area in Connecticut, but had been preserved only near the trap, 
where it was hardened (62). But here, as before, it may be urged that 
as hard sandstones occur plentifully in regions free from eruptive rocks, 

it is more probable that variations in the hardness of the sandy and 
shaly Triassic strata, except those close to the trap, are due to the un- 
equal action of the ordinary processes of consolidation. Whatever dis- 
tinct hardening effect was produced by the trap, it generally extended 

but a short distance into the adjoining rocks, 
than one hundred foct. 

probably in no case more 

Slight mineral alteration reached farther than 
any other notable change. 

The marked difference between the effects of the intruded and the 
overflow sheets has already been pointed out. The Palisade trap (H, J) 
liardcned the adjoining sandstones and shales very distinctly for twenty 
feet and probably farther, and in some of the more easily altered layers 
produced a marked crystalline structure : this was equally apparent at 
upper and lower contacts. On the other hand, the lower contact of the 
ovei'ffows shows a very slight change from the normal sandstone. " Em- 
erson describes the alteration under the Greenfield trap as extending 




■ t 

only an inch from the contact, and the baking as reaching only a foot 
(196). Under Mount Tom (B), the baking reaches three feet or more. 
Under the First Mountain trap at Paterson (L), the alteration is dis- 
tinct for several inches. 

The different effects in these contrasted cases evidently depend on the 
manner and rate of cooling. The intruded sheets must have cooled 
slower, and entirely by conduction through the enclosing rocks, and 
hence produced more baking than the others. The difference in the 
baking effects of different intruded sheets can probably be largely re- 
ferred to the variations in the composition and the amount of moisture 
present at the time of intrusion. 

Tilting of the Sanddoiies and Traps. ■ — The remarkable monoclinal 
structure of several of the Triassic belts has given rise to five supposi- 
tions : first, that the present is the oi'iginal position of deposit; second, 
that the originally flat layers have been tilted into a monoclinal without 
faulting; third, that certain paired belts are lateral remnants of a broad, 
eroded anticlinal ; fourth, that the present position is the result of re- 
peated faults and moderate folds; fifth, that a tilting was in progress 
during the deposition (Cook, h, 174; c, 34). I am unable to give any 
evidence for or against this last proposition. 

Before speaking of these theories we may note the structure of the 
several Triassic belts ; for some of them do not present any very peculiar 
features in the position of theiV strata. On Prince Edward Island the 
formation shows repeated faint folds (Dawson and Harrington). Around 
the Bay of Fundy there is an unsymmctrical synclinal, with the greater 
visible part on the southeast. The Connecticut valley belt has a pre- 
vailing dip to the eastward, but with significant exceptions. The long 
strip from the Hudson extending almost continuously to the Dan Eiver 
in North Carolina has a similarly prevailing dip to the northwest or 
west, but also with certain irregularities. The llichmond coal field is a 
synclinal, strongly faulted (W. B. Bogers and neinrich). Two patches 
north and east of it, and the Deep Iliver strip reaching into" South Car- 
olina, dip to the east or southeast (Heinrich and Kerr). 
■ First Theory. — H. D. Eogers first thought that some external force 
was responsible for the tilting (a, 160), but soon replaced this supposi- 
tion with the theory that the several sandstone belts from the Dan Bivcr 
to the Hudson had been deposited with their present oblique dip in a 
noble river that rose in the mountains of North Carolina and flowed 
northeast to the ocean about New York Biiy; that the occasional rever- 
sal of dip was produced by eddies in the great current; and that the 

ft i 



ment against it. 

monoclinal theory was impossible because the great depth that it re- 
quired for the sandstone was disproved by the visibihty of the old foun- 
dation rocks at certain points within the Triassic belts {h; c, 166-171 ; 
d; g, 671, 7G1). Mather replaced the river by ocean currents, but oth- 
erwise accepted this explanation. Whclpley thought the largo and small 
sandstone areas of Connecticut once connected by a general, oblique 
deposit, since eroded except where trap intrusions preserved it. This 
theory has gained few advocates. Oblique deposition on so large a scale 
and at so uniform a dip as sometimes occurs over large areas is impos- 
sible ; and as has already been pointed out, the occurrence of plentiful 
conglomerates on the dip side of the sandstone belts is a strong argu- 

The unsymmetrical form of footprints, as if made on 
a sloping surface (IL D. Rogers, d), is too exceptional to be of much 
value (Hitchcock, h, 17). On the other hand, it need not be claimed 
that the layers were absolutely horizontal when formed. Some small 
share of their present dip may be original. 

Second Theory, — The theory of anticlinal remnants was first proposed 
for North Carolina by Kerr, in 1874. It was extended by Bradley (289) 
to Connecticiit and New Jersey, in 18 76, and proposed for the same 
region independently by Russell, in 1878. Heinrich suggests a some- 
what similar explanation for the several sandstone patclies in Virginia 
(249), but later considers each estuary isolated (251). The objections 
to this theory arc well set forth by Dana {g)] it has the serious defect 
of resting on negative rather than positive evidence; it fails to explain 
the general absence of trap in the intermediate region, and the occur- 
rence of such an isolated sandstone patch as that of Waterbury, Conn.; 
the amount of erosion it requires is something enormous ; the occurrence 
of conglomerates along the outcrop side of the sandstone belts has already 
been mentioned as arguing against it. (See fig. 29.) 

The Third Theory supposes the entire body of horizontal strata tilted 
to a uniform dip, and the upper parts worn oE This has been advocated 
by Hitchcock (c, 221, and later), partly by Cook (&, 174), and more re- 
cently and decidedly by Leconto (441). Besides the great thickness of 
strata that this supposition requires, and the enormous erosion it involves, 
not only of sandstones but of the older rocks on one side, the theory is 
based on the assumption that there is no faulting or reversal of dip ; and 
this is not proven. If lack of visibility sufficed to prove the absence of 
faults, it might be said that there are none in Pennsylvania, Virginia, 
and Tennessee; for fault-planes are hardly ever seen there; they are 
lines of weakness, and are always covered with detritus. Their exist- 



ence is known by the repetition of outcrops that they produce, and this 
test can hardly be apphed as yet in the Triassic belts, for the beds there 
are, as a rule, too little varied to be recognized at their repeated appear- 
ances, if such occur. On the other hand, as may be inferred from the 
position of the intruded sheets, there is evidence that, however numer- 
ous the faults may be, they fail to bring up the lowermost strata; and 
the great sweep of the trap curves in New Jersey would indicate an ap- 
proach to the simple monoclinal structure. These considerations would 
imply a great thickness f'-r the sandstone. (See figs. 6 and 28.) 

The Fourth Theory looks on the general monoclinal dip as the result 
of tilting with faulting and some slight folding, but is unable to explain 
the mechanism of the disturbance ; and here with regret I must take 
my place. Much more observation is necessary before any detailed ex- 
planation of- this peculiar disturbance can be made. It can now be said 
only that the disturbing force pretty surely was one of the latest mani- 
festations of the Appalachian mountain-building, which began and had 
its greatest activity long before ; and that the eruption of the trap had 
no important share in it. Here, as in so many other cases, the trap is 
relegated to a passive r(}le; and as already suggested, its eruption was 
very probably a direct effect of the force which at one time depressed 
the Triassic troughs, and later deformed the rocks collected in them. 

It is sometimes objected that it is mechanically impossible to fault a 
series of horizontal layers into repeated parallel monoclinals. In an- 
swer to this it should be urged that too little is still known of geological 
mechanism to make such apparent impossibilities of much importance ; 
that faulted monoclinals of gentle dip have been found in the Western 
plateaus (see Button's sections of the High Plateaus of Utah), and or 
steeper dip in Tennessee (Safford's Geology of Tennessee); and that the 
Triassic monocbnals show not infrequent irregularity too great to be 
considered the result of eddies (as Kogers thought), and implying the 
presence of incipient folds. 

As to the occurrence of faults, some of small throw are seen in Delany's 
Quarry *above Holyoke (B), in the West Springfield railroad cut (C), and 
on the northern slope of Garret Eock, Paterson (L); slickcnsides are 
noted about New Haven, in the Jersey City cut, and in Goat Hill by 
Lambertville. Faults are also shown in the Eichmond coal field syn- 
clinal by W. B. Eogers and Heinrich, and are suspected by Cook in New 
Jersey (c, 33). Further observation will surely discover others, either 
directly or by means of repeated outcrops. In this latter way a fault 
has been determined with a great degree of probability at Bcckley, 





Conn. (D) ; and a similar one, but of much larger throw, very likely 
occurs west of Lamentation Mountain, Conn., with uplift on the east, 
so tliat the trap sheets seen in Lamentation and m the Hanging Hills 
are really parts of a single overflow. The evidence of this is the repe- 
tition of similar series of strata as described by Percival in the outcrop 
fiices of the two mountains ; in each there is sandstone at the base, then 
the amygdaloid of the anterior ridge, next a limestone at the bottom of a 
shale, and finally the heavy trap of the ridge line. As shown in fig. 43, 
the fault is about three thousand feet. It is obvious that a great sav- 
ing is thus made in the thickness of the sandstone : a moderate depth 
of formation is made to cover a good breadth of country by its repeated 
rising to the surface ; the layers do double dnty^, and the vast thickness 
supposed necessary on the monoclinal theory may be much reduced for 
Connecticut at least. Similar evidence makes it very probable that the 
same sheet of trap is repeated by faulting and folding southward from 
Lamentation Mountain in all the high ridges to that of Saltonstall Lake ; 
but further observation is needed on this point. 

We have already stated that the uniformity of dip in direction and 
amount has been exaggerated, especially by H. D. Rogers, who wrote 
that in the Connecticut valley there is "only one direction of the dip," 
and in New Jersey, Pennsylvania, and Virginia, " without exception the 
strata dip in only one direction" {g, 1Q>1; also G70). It was thus that 
he was forced to prefer the theory of original oblique deposition. But 
this artificial constraint vanishes when we recognize that fiat folds with 
faults are perfectly indicated by the curved outlines of the trap ridges, 
and by the conformity of the sandstones to these curves; for the trap 
sheets that are shown to be overflows at once take the important position 
of distinct horizons in the monotonous sandstones and shales, by which 
distortion can easily be recognized ; just as the scalloped line of outcrop 
of the Medina sandstone reveals the folded structure of the Appalachians 
in Pennsylvania, 

The conformity of the sandstones to the curved trap ridges is well 
known, but has never received its proper explanation. Percival de- 
scribed the trap ridges as "arranged according to a peculiar system, 
conformably with which the secondary rocks are themselves arranged" 
(10). "Tlie trap ranges .... conform, in their arrangement, to that of 
the sandstone, and indeed have apparently exercised a controlling influ- 
ence on the arrangement of the latter, thus indicating a cotemporary 
origin" (321 ; also 299, 408). He further says that both the general 
and particular direction of strike of the sandstone strata agrees with the 

VOL. VII. — KG. 9. 




trend of the trap ridges (430-432). Hitchcock noted the same arrange- 
ment for Massachusetts (e, G54 ; A, 17, and PI. IL); and Cook mentions 

it for New Jersey (c, 29, 32). 

An iUnstration of a flat fold producing a curve may be. scon in the 
excellent example at Beckley, Conn. (D) ; it corresponds perfectly with 
the much larger curves shown by the Turner's Falls — Deerfield Range, 
by the great ningQ from Bclchcrtown, Mass. to Meriden, Conn., by 
many other smaller ranges iu Connecticut so well shown on Torcivars 
beautiful map, and by several similar curves in Now Jersey. The most 
instructive region for the further study of this important point in the 
structure of the Triassic belts is without doubt the southeastern corner 
of the Connecticut sandstone area, about Durham and North Branford, 
PercivaPs "volcanic focus" (311). I had hoped, but was unable, to 
reach it during the past summer. 

All these folds are like flat oval dishes, tilted toward and faulted on 
the dip side of the general monoclinal; and as a necessary consequence 
of this, the trap sheets that are folded with the sandstones outcrop in 
crescen'tic ridges with the horns of the crescent pointing in the direction 
of general dip.* The fact of this position was first pubhshcd by Percival 
in 1842 (311), but its cause was not then perceived. The folds are 
very numerous in Connecticut, but in Massachusetts and New Jersey 
they are fewer and larger : this would indicate that in the last two States 
there is the nearest approach to the simple monoclinal of the third 
theory of disturbance. An interesting exception to the rule occurs east 
of Saltonstall Lake, Conn.; it is P. 2 of E. I. of Percival's notation, and 
is described as abrupt on its eastern, convex side (325) : this makes it 
seem very much like the eastern edge of a small sheet whose western 
outcrop is lettered P. 1 on Percival's map. Whether the small curves 
in southern Durham lettered P. 1 of E. TIL are produced by folding, or 
result from the original form of intrusion or overflow, or are simply the 
effects of erosion, requires further observation to determine.t 

In regard to the cresccntic form of the trap ridges, H. D. Eogers con- 
sidered it natural that the horns of the curves should point with the dip 

* The imitation of this crcsc.ntic line of outcrop produced at a cross valley is men- 
tioned under the observations at Beckley. 

t It is greatly to be regretted that Percival had not the facihties for illustra ion 
afforded now by well-executed chromo-lithography. A mn.p of the Connecticut valley 
drawn with as full an appreciation of topographic form as Percival must have pos- 
Bessed, and colored to show the different varieties of trap and sandstone, is needed to 
do justice to the remarkable features of this uni-iue region. There is nothnig hkc it 
known anywhere else in the v.'orld. 

» • 



of the sandstone ] for as a trap sheet made its way obliquely ai)ward be- 
tween the layers, the cover of the sandstone must have been cracked at 
the ends, allowing the trap to rise there and so turn the extremities of 
its outcrop with the dip of the bedded rocks (e). This was agreed to by 
Silliman, Jr. Whelpley thought the crescent ridges determined by the 
form of the fissures in the old rocks below the sandstones (64). Dana 
considered the curved ridges as marking curved fissures, characteristic 
of certain eruptions, and further added that the agreement in form of 
these ridges with more prominent features of the confirms " the 
view that ranges of mountains and islands correspond to ranges of 
fissures " {a, 391, 392) ; but later {h, c, 21) he essentially follows Rogers's 
explanation, and further says that the tilting was caused by the subsi- 
dence of the estuaries, and is "without evidence of folds "(c, 421). 
Wurtz considers that subsidence went on to a small amount during 
deposition, and was fastest along the axis of the belt. *' Such slight 
inward inclination of the beds on both sides of the basin, explains the 
crescent form of the edges of the sheets of trap. The flow or propaga- 
tion of the mctamorphic agent being thus governed." (102.) Russell 
calls the curves "lines of least resistance," wdiich were naturally and 
necessarily chosen by the eruptive trap (c, 241). Cook says, " The prin- 
cipal changes of dip appear to be, in some unexplained way, connected 
with the direction of the trap ridges, and are near them" (c, 20). All 
of these explanations, based on the intrusive origin of the trap, fail "when 
the sheets are found to bo overflows. 

The, value of the overflow sheets as marking horizons in the sandstone 
formation is thus very considerable, arid will in time lead to closer meas- 
ures of thickness than have yet boon possible. The peculiar restriction 
of the localities of footprints in the Connecticut valley to the strata 
along the back of overflows is well shown by Hitchcock in the map in 
his Ichnology : it is evidently connected, as he suggests, with the appear- 
ance of volcanic islands and shallow waters in the old estuary. 


The Triassic strata were deposited nearly horizontal in narrow estu- 
aries not greatly exceeding their present area : son^c degrees of their dip 
may bo the result of original oblique deposition, but this is insufficient 
to explain all of it. During their accumulation, extensive and repeated 
eruptions, vei'y possibly from fissures, poured sheets of trap over their 
surface, to be buried under later deposits ; i?,nd at the same time, or later, 



large and small trap sheets were forced laterally between the deep-lying 
strata. The period of deposition, and probably of eruption, was ended 
by an uplift that drained the sandstone areas, and tilted the included 
strata by small amounts from their original position. Some of the strips 
were bent into simple or faulted synclinals (Nova Scotia, Richmond coal 
field) ; one was thrown into gentle waves (Prince Edward Island) ; the 
others received- their peculiar monoclinal tilting. Why the general 
monoclinal structure was produced cannot now be clearly explained ; 
but by means of the overflow trap sheets, which serve perfectly as iden- 
tifiable horizons in the monotonous sandstones and shales, it can be 
shown that there are distinct folds in these monocllnals, thus explaining 
the crcsccntic form of the trap ridges. The folds are of small pattern 
in Southern Connecticut; on a much larger scale in Nova Scotia, Massa- 
chusetts, and New Jersey. Faults also occur : some of small throw are 
directly visible ; some of much greater displacement arc properly inferred 
from the repetition of similar scries of strata ; and many more probably 
exist hidden under drift and soil : thus the necessity is avoided of sup- 
posing a great thickness for the formation. The erosion of the sedimen- 
tary and igneous strata into their present form was probably accomplished 
in great part during a time of greater land elevation than the present; 

but it presents nothing abnormal. 

The physical features of the Triassic belts that seem most worthy of 
further observation are, first, a closer identification than has yet been 
made of the source of the conglomerates that not unfrcquently occur 
along cither margin of the belts, thus allowing or excluding the ideas of 
original oblique bedding and of anticlinal remnants; second, the deter- 
mination of the overflow or intrusive origin of the many undetermined 
trap ridges; third, the further proof that the curvature of these ridges 
implies a folding of the strata; fourth, the closer identification of the 
surmised but undiscovered faults. 

Camcridge, January 8, 1883. 




Tins article is accompanied by three plates, numbered IX., X.,and XL, witli fifty- 
two figures, numbered coiisecutivGly. 

Plate IX., figs. 1-31, gives u general graphic review of the opinions held concerning 
the relations of the trap and sandstones from 1818 to 18^0. The references to the 
originals of the drawings are given on pp. 280, 281. 

^ Plates X. and XI. Sketch-maps serving as guides to the localities of the observa- 
tions above described, and figures representing some of the results obtained. Page 
numbers refer to explanations in the text. 

Kig. 32. Turner's Falls, M^ass. Fig. 33. Section of trap ridges (p. 259). Fig. 34. 
FraguKints of trap in overlying sandstone (pp. 2G0, 300). 

Fig. 35. About Mount Tom, Mass. (p. 261). Fig. 36. Section of Mount Tom and 

posterior ridge (p. 261). Fig. 37. Generalized section of contact, Delany's Ouarrv 

(p. 262). ^ 

Fig. 38. Kailroad cut in posterior trap ridge. West Springfield, Mass. (p. 263). 

Fig. 39. Map and section of curved trap ridge at Beckley Station, Middletown 
Branch Railroad, Conn. (pp. 264, 265, 306). 

Fig. 40. The Hanging Hills from Meriden (p. 265). Fig. 41. The same in section 
(p. 266). Fig. 42. Map of the same (p. 266). Fig. 43. The same with Lamentation 
Mountain, as seen from Wallingford, Conn., showing place and throw of probable 
fault (pp. 2G6, 305). 

Fig. 44. Dikes near East Haven, Conn. (pp. 268, 292). 

Fig, 45. Side of ragged dike, Wallingford, Conn. (p. 26G). 

Fig. 46. Base of Palisade trap cutting sandstone, Weehawken, N. J. (p. 270). 

Fig. 47. Garret Rock, First Mountain, Paterson, 1^. J. (pp. 273,304). Fig. 48. 
Gorge at Passaic Falls, Paterson (pp. 272, 300). 

Fig. 49. Pecidiar conglomerate overlying First Mountain tra^"), Feltville, N". J", 
(p. 275). Fig. 50. a, b, the same, natural size (p. 275). 

Fig. 51. Intruded trap sheets, Martin's Dock, below New Brunswick, N. J 
(pp. 276, 295). 

Fig. 52. Intruded trap sheets, near Point Pleasant Station, Belvidcre Railroad, 
K. J. (pp. 277, 295). 


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The UeUo'ype Printing Cc^xSlTrauont .Se^jijo 


No. 10. — The Folded Ildderbcrg Limestones Hast of the Catsldlls. 

By William Mokris Davis. 

Intro(luctory. — Previous Descriptions. — Character and Sequence of tlic Formations. 

Hudson Mver Group. — Absence of Medina ^Niagara Group. — Waierlmu and 

Tentamlite. — Lower Fentmnerus Limestone. — Calskill Shaly Limestone. — Uncri- 
nal and Upper Pentainerus Limestone. ~ Oriskany. — Gornifcrous Grits. — Gornif- 
erous Liinesione. — Marccllus Shale. — Hainilton and Catskill Sandstones. — The 
Question of Unconformity. — Paleogeography. — Folds and Faults. — The Catskill 
Gorge below Leeds. — Other Points for Observation. ~~ Unconformity by Faulting. — 
Gompression in Synclinals. — Gompression in Faulting. — Surface Geology. — Gla^ 
cial Phenomena. — Stratified Glays. — Former Lines of Drainage. 

The Appalachian district in Pennsylvania is made up of three well- 
distinguished parts : a plateau of nearly horizontal rocks on the north- 
west, showing no formation younger than the Carboniferous and Upper 
Devonian ; a rolling low country on the southeast, where the rocks are 
Lower Silurian and older, greatly folded and often half or wholly crystal- 
line ; an intermediate region, where the wave-like folds of the Paleozoic 
strata arc best developed, and their effect in producing anticlinal, syn- 
clinal, and canoe mountains is best seen. If we trace those three belts 
northeastwardly into the Hudson valley, the fu'st is well shown in the 
broad mass of the Catskills ; the second in the perplexing Taconic region 
from the Hudson across to Western Connecticut and Massachusetts; 
but the third, so striking in Pennsylvania, has dwindled to a narrow strip 
of insignificant hills, only a mile or two wide, and a few hundred feet in 
height. Although so greatly reduced in size, this middle belt still re- 
tains its characteristic structiu*e very clearly, and reveals this structure 
in its surface forms. The accompanying map represents a part of it 
some ten miles in length, the middle point of which is about west of the 
town of Catskill on the Hudson. Very little attention has as yet been 
given to this belt of miniatvu"e mountains, excepting in the study of its 
fossils. The following are the only descriptions referring to it that I 

have found. 

W. W. Mather. Geology of New York; First District. 'Albany, 
1843, pp. 317-352, 3GG-421. A general description is given of tKe sev- 
eral formations here occurring, their characters and sequence ; but the 
structural peculiarities of the district are very imperfectly represented. 

VOL. VII. — NO. 10. 



E. Emmons. 

Agriculture of New York. 

Albany, 1846. Vol. I. 
pp. 134-175, and Plates IV., XX., and XXL, bear more or less directly 
on the structure of our district. 

N. S. Slialer. On the Existence of the Alleghany Division of the 
Appalachian Range within the Hudson Valley. American Naturalist, 
XL, 1877, 627, 628. A short notice of the extension of distinct anti- 
clinal and synclinal structure to this point. 

W. M. Davis. The Little Mountains * cast of the Catskills. Appa- 
lachia. III., 1882, 20-33. A detailed elementary account of the struc- 
ture of a small part of the Hclderbcrg belt; with map and sections. 

No geological maps of this region have been drawn on a large enough 
scale to show anything more than parallel strips of color along the west- 
ern side of the Hudson valley. The little sketch-map in the last of 
the above-named articles, and the map accompanying this paper, are the 
first that show the welLmarked Appalachian topography of the district. 

The material for the present paper was obtained in part during two 
short visits in the spring and summer of 1877, the first in company with 
Mr. E. li. Benton, now Professor of Natural History in the University 
of Rochester; the second with Professor N. S. Shaler, Mr. J. S. Diller, 
and members of the Harvard Summer School of Geology. But a third 


trip made in the spring of the present year furnished fuller results ; in 
this I was accompanied by Mr. J. E. WolfP, Assistant in Geology, and by 
Messrs. Bunker, Chase, Clark, Dean, and Jackson, students in Harvard 


College and the Lawrence Scientific School. To all of these I desire to 
give thanks for aid in making the observations heroin recorded. 

Our work was mostly stratigraphical, and some description of part of 
the results has already boon published in Appalachian as above men- 
tioned. As only a short time was spent on the ground, the reader must 
expect to find some points indicated as probable, but not fully estab- 
lished ; many of these would afford excellent subjects for detailed sum- 
mer studies, and I should be greatly pleased to learn of their being taken 
up by residents or summer visitors. 

The Silurian and Lower Devonian strata occurring in this part of the 
Hudson valley are the Hudson River sandstones and shales in the low 
country on the east by the river, and in occasional anticlinal valleys 
within the Little Mountain belt ; next, the Lower Ilelderberg limestones, 
in good variety and well exposed at many points ; over these the grits 

* This name was given by the writer to call attention to tho peculiarly mountain- 
like structure and form of these limestone lulls. They are not so known in their own 

« h 



and limestones of the cornifcrous period ; then the Marcellus shale in a 
valley^ and the Hamilton sandstones in a line of bluffs limiting our dis- 
trict on the west. The latter sandstones or very similar ones continue 
to the foot of the Catskill Mountains in low ridges and shallow meadow 
valleys. Whatever paleontologieal evidence might be discovered by de- 
liberate observation to justify these subdivisions^ the lithological char- 
acter is so distinct that fossils are hardly necessary, except in some of 
the limestones, for the identification of the several groups. The follow- 
ing table shows the sequence and thickness of the strata as described 
by several observers here by Catskill and a little farther south near 



Upper Pontamcrus and 

CatskiU Shaly- 

Lower Pentamcrus- 

(Uppcr UibboTi.) 






gritty shales. 


aandy lime- 

Heavy and 






impure slialy 



j~-^ Spungedayei', 

i=:^5 Fini! bedded. 

nud^un lUver Group. - JZIE ' ■ ^' '^^' j^li:^' ' '^- 

h , J 

'^^^^^'ITTrTvTZLJe'i' ■ '/ ■ ' ii 

Shaly linic- 

Khales and 
line sand- 



<' to 









1870. * 












? 100 






* As referred to below, page 321. 




The remarkable absence of the Medina-Niagara series of formations 
between the Hudson Eiver group and the lowest of the overlying lime- 
stones will be discussed farther on. Here by Catskill nothing was seen 
that could be surely referred to any of the missing formations ; but 
Lindsey and Dale describe six or eight feet of Coralline or Encrinal 
liuicstone that they identify as some member of the Niagara scries. 
The absence of the Oriskany sandstone is almost as complete. 

The formations observed in our sections of the Little Mountains may 

be described as follows. 

The Hudson Eiver group consists of a great scries of fine gray or 
brown sandstones and shales, with no layers here sufficiently marked to 
be recognized at their probably repeated outcrops. The layers some- 
times contain Hakes of many-colored clay with the fine sand, implying 
an erosion near the place of deposition, and some layers have an uneven 
surface like a mud-flow (see fig. 1). Irregular ripple-marks are common, 
and in good exposures they may be seen over large surfaces; but wo 
found no cross-bedding or coarse sandy layers. No fossils were seen : 
their absence cannot be ascribed to metamorphism, either mechanical or 
chemical, for many of the strata seem \Gry little altered in spite of the 
general disturbance. These rocks are well exposed at many points 
where they crop out above their usual terrace covering of clays and 
sands that are spread over all the low land ; and arc also shown on the 
creek sections, as on the bank of the Catskill at Catskill Village, where 
excessive and irregular plications may be seen (fig. 2) ; sharp folds, 
slickcnsides, and small faults are very common; and likely enough 
fliults of larger throw occur, though they cannot be detected. A point 
of good continuous, and just now of fresh exposure, is in the railroad cut 
on the bank of the Catskill just below Austin's Mill; a fine dome-hke 
fold is seen by the stream, and farther on broadly curved surfaces of 
rippled shales alternating with firm sandstones dip conformably under 
the limestones (fig. 3). Unconformity might well be expected : the 
Medina, Clinton, Niagara, and Saliua series, about one thousand feet 
thick in Western New York and over six thousand in Central Tennsyl- 
vania, are all absent here, unless some few feet of nondescript beds may 
represent them.* The evidence of conformity and the possible mean- 
ings' of this absence of formations are discussed farther on. 

The beds of passage from Hudson River to Lower Hclderberg were 
best seen on the road leading down to Austin's Mill (fig. 3), and at the 

* If tlie shaly Layers of the Watcrlime are considered equivalent to the Saliua, 
this mubt be a little modified. 

museum: of comparative zoology. 


north end of the Quarry Hill : they arc sandy limestones, without fossils 
as far as observed, and not more than five or ten feet thick between char- 
acteristic Hudson Eiver sandstones and shaly layers of the Waterlime. 

There is no distinction attempted on our map and sections between 
the Waterlime and the Tcntacnlite hmestone : all the calcareous layers 
below the knotted strata of the Lower Pentamerus are marked by a 
single color. Professor Hail (Paleontology of New York, III.^ 386) 
describes the Waterlime as being of " gray or drab-colored surface and 
darker interior color, and almost destitute of fossils" ; while the Ten- 
taculite is "a thinly bedded blue or black limestone, abounding in 
certain organic remains." These characters are easily recognized. The 
total thickness of seventy feet was measured on the eastern slope of the 
Quarry Hill, from the uppermost sandstone to the lowest knotted lime- 
stone. At Austin's Mills the measure would be less. The subdivisions 
of the Tcntacnlite, as described at Kondout (see Lindsey and Dale, aa 
below), arc here clearly made out. Some ten feet of fossilifcrous lime- 
stone are followed by the Strumatopora layer, of one or two feet tbiek, 
with numerous sponges a foot or a foot and a half in diameter (fig. 4) ; 
next above come twelve feet of fine Pibbon limestone, in even parallel 
layers, shown by alternating bands of lighter and darker color, often aa 
thin as one twentieth of an Inch ; then comes the coarse Lower Penta- 
merus, but about ten feet above its base thpre is a band of Eibbon 
limestone again, one or two feet thick. The oven lines and smooth 
gray weathered surface of the Ribbon limestone frequently serves as a 
welhdetermined horizon, outcropping on the slope of the ridges made 

by the Lower Pentamerus. 

The fossils of the TentacuHte limestone commonly seen are a Leper- 
ditia, a Tentaculiie, Orthis plicaia, and a Turritella (?), The first two are 
very common on certain layers. The thickness of the Waterlime and 
Tentaculite has already been mentioned as seventy feet or less. These 
two divisions of the limestone group are well seen — at least their upper 
members — at many points along the front of the Kalk Berg, around 
the synclinal outlier opposite Austin's Mill, and at the head of tho 

southern anticlinal valley. 

Tho change to the coarse, heavy, knotted layers of the Lower Pen- 
tamerus is accomplished within two or three feet. With this comes 
tho frequent occurrence of dark chert iu irregular masses up to six 
inches in diameter. The fossils easily found arc Fentainerus galeatm 
(beaks arc very common on -weathered slopes in the soil) and Atry^ya 
reticularis: both are common. The thickness measured about eighty 



feet on the eastern slope of the Quarry Hill. The best exposure is on 
the Catskill on the first bend above Austin's Mill, where broad surfaces 
of the limestone are laid bare ; it is fairly shown in the ridges or bluffs 
all along its outcrop. 

The Catskill (formerly Delthyris) shaly limestone is a rather evenly 
bedded, thin splitting, impure dull blue rock weathering gray or brown 
as its calcareous particles disappear. Fossils are very common, but on 
weathered outcrops arc found only as casts : the ordinary forms are 
Spirifer macropleuraj Spiriferina perlamellosa, Streptorhy^clms {Ilemu 
pronites) radiatu.% Stropkomena rhomhoidalis, Ehynchonella ventricosdy 
Eatonia peculiaris, and Pterinea com'munuf^ The thickness of this 
division is somewhat under one hundred feet. The best exposure is at 
the railroad bridge across the Catskill, three quarters of a mile below 
Leeds, and on the banks farther down stream ; but characteristic fossils 
are easily found at many points. 

The shells recognized were 

The Encrinal and Upper Pentaracrus limestones were not separated 
in our study, as they constituted a single topographic element ; but it 
was readily seen that crinoid stems were more plentiful in the lower than 
in the upper layers. The rock is hard, heavy-bedded, and coarse-grained, 
consisting of broken shells and crinoid stems; it is well adapted to 
heavy masonry; on some weathered joints, exposed in Frenches Quarry, 
very clear cross-bedding was seen. Corals make no important share of 


the^e limestones so far as we could discover. 
Pentamerus pseudo-galeatuSy Spirifer cydoptera^ and many others not de- 
termined : they are so firmly held, that it is difficult to break out good 
specimens. The thickness of these two members as determined at the 
railroad bridge below Leeds is one hundred and twenty feet, but this 


may be exaggerated by local faulting. Other observers give it much 
less. French's Quarry and the Catskill bank by the railroad bridge give 
good exposures ; and fair outcrops arc found at many other points. 

These Lower Helderberg limestones as a whole are decidedly harder 
than the shaly sandstones below or the grits above them, and are strongly 
determinant in forming ridges and bluffs. Among the most marked of 
these is the long, continuoTis ridge at their easternmost outcrop, known 
as the Kalk Berg (corrupted into Kalla Barrack f), where they are usu- 
ally nearly vertical and sometimes are overthrown : other interesting 
forms of outcrop appear on the several synclinal and anticlinal folds. 

* The names are thus given in the collection in the American Museum of Natural 
History, New York. 

t For these local names I am indebted to Mr. Henry Brace of Catskill. 

\ I 

X -^^xx -rAmr. n ^^-j n 

- -*-■ ■- ^ir_-B^-»nr ^^ ^r^i *"i-C 

* 4 



The subordinate ridgc-making members of the group are well shown in 
the Quarry Hill synclinal ; they are the Lower Pentamerus, the upper 
part of the Catskill Shaly, and the Upper Pentamerua ; while the Water- 
lime, the junction of the Lower Pentamerus and Catskill Shaly, and of 
the latter with the Encrinal, are marked by depressions. These relations 
of hardness are pretty constantly shown in all parts of our field, and add 
much to the ease of identification of the several subdivisions. 

The upper part of the Upper Pentamerus becomes sandy and impure 
for about ten feet : this change is completed in the occurrence of a six- 
inch layer containing limestone pebbles up to an inch in diameter, and 
quartz grains of a quarter of an inch or less. Although no fossils were 
found in this thin conglomerate, I have considered it as representing the 
Oriskany sandstone, as it has the proper place in the series. Mather 
and Emmons describe it as half a foot to two feet thick. The best ex- 
posure of this layer was found on the north bank of the Catskill at 
Leeds, in the vertical strata on the western side of the anticlinal that 
shows there in the stream ; and again at several points below, as far 
down a'B the railroad bridge. 

The Grits which come next are fine-grained, dark gray or bluish, and 
generally with all appearance of bedding destroyed and supplanted by 
an imperfect, nearly vertical cleavage. Bedding planes are sometimes 
found, and generally contain impressions of the Spirophyton cauda-galli. 
Very few other fossils were found in this monotonous formation. Its 
thickness is three hundred and fifty feet, when measured by the breadth 
of outcrop where the enclosing limestones were about vertical, east of the 
limekiln near the junction of Old Kings and the Mountain roads. Other 
observers give only a fifth of this thickness. Outcrops are generally 
poor, as the rock usually weathers down to a rolling surface of gray 
gravelly soil, or is covered by swamps; the lower half of the Grits is 
more easily eroded tlsan the ujlpcr : the gorge of the Catskill by Leeds 
pi-esents on its southern bank an excellent section of the entire forma- 
tion (fig. 5), and exhibits perfectly the relation between its true bedding 
and secondary fracturing. A small table-rock, over which a little stream 
falls on its way to the Kaatcrskill west of West Eerg, an eighth of a 
mile north of the limekiln above mentioned, shows many slabs near tlio 
top of this formation well marked with the cocktail seaweed. 

The Corniferous limestone follows the Grits by an abrupt change ; its 
layers are often massive, and always of a fine, close grain. Dark horn- 
stone is very common in irregular masses often a foot broad ; it is clearly 
of secondary origin. Fossils are scarce ; the corals so common farther 




west are hardly seen here, but the fine, massive limestone was very pos- 
sibly largely derived from a coral reef not far distant. There was no 
good place to estimate its thickness; but twenty-five or thirty feet, as 
given by Emmons, seems too small. The margins of this formation have 
a peculiar way of weathering out into large loose blocks, often ten feet 
cube ; good examples are seen on Old Kings roa^d just south of the 
Mountain road ; near Van Luven's Lake ; and north of Hooge Berg. The 
last-named point gives a good section of the limestone at its southern 
end, and it can be well seen at Leeds west of the Grits. 

The Marccllus shale follows by a very abrupt transition, as may be 
seen at its only exposure, on the east bank of the Cauterskill, just south 
of the Mountain road bridge. It is a fine black fissile shale, in which a 
few faint fossil shells were found in 1877. Its upper limit and thickness 
were not determined, as it is throughout worn down into a valley be- 
tween the Corniferous on the east and the Hamilton on the west, and 
deeply buried under stratified clays. The Hamilton sandstones and 
shales and the overlying formations were not examined closely; the 
lower layers of the former arc well shown at the Big Falls of the Kaa- 
terskill, where several strata are very fossiliferous ; Spirifer miicronata 
and medialis are both of common occurrence. From the Marccllus val- 
ley to the foot of the mountains these and similar, but non-fossiliferous, 
sandstones and shales continue with a gentle westerly dip, and their 
thickness must amount to over two thousand feet. From the foot of the 
mountains to the summits of their broad masses, the strata are essen- 
tially horizontal, and may measure about three thousand feet more, 
chiefly of sandstones and sandy shales, with some conglomerates near 
the top. These are generally accounted of the Catskill formation. 
Cross-bedding is common throughout, and in a great part of the Hamil- 
ton group. 

The most interesting question presented by this scries of rocks turns 
on the absence of the Medina, Niagara, and Salina strata from between 
the Hudson Kiver and the Lower Helderberg formations, and the possi- 
bility of unconformity at this point of the section. The following his- 
toric review will show what observations have been made and what 
views have been held on this subject in the Hudson valley. 

W. W. Mather. Report of W. W. Mather, Geologist of the 1st Geologi- 
cal District of the State of E"ew York. Albany, 1838. (2d Annual Re- 
port.) "Mount Bob and Becraft's Mountain are outliers of limestones, 
lying unconformably upon the subjacent slate rocks. I have tj-aced these 
rocks within a few feet of their junction in many places." (p. 1G5.) 

t t 



The same. Fourth Annual Ecport, 1840. The Hudson Hiver slate 
group "is overlaid unconformably in many places by the various rock 
formations of more recent origin." (p. 212.) The common and hydraulic 
limestones at the base of the Hclderberg series "sometimes rest uncon- 
fcirmably upon the Hudson slate group, as at Lawrence*s quarry, on the 
Kondout, opposite AVilbur (see fig. G, copied from fig. 1, PI. 2G, Final 
Eeport, 1843); sometimes conformably on the Shawangunk grit, .... 
as at Rosentiale a,ud Lawrencevillc, on the Kondout-; sometimes on the 
red and variegated sludes and grits that overlie tlie Sliawangunk grits, as 
at the High Falls of the llondout in Marblctown." (p. 237.) Lawrence's 
quarry is again mentioned (242) as affording "a fine exposure of the 
different strata^, and tlie Hudson slates are seen unconformable, beloAV 
the limestones." At Hasbrouck's quarries on Pino Mountain between 
llondout and Kingston Point, tlie Hudson slate series dips 40-GO^ to 
E. S. E. ; the overlying limestone and cement beds dip 80° W. N. W., 
"and this dip continues nearly \miform along this line of upheave to the 
*High Hocks' above Kingston Point." (p. 242.) 

The same. Fifth Annual Keport, 1841. There is " a line of fracture 
and anticlinal axis" extending northward from New Jersey, passing 
Kingston and the district here mapped. " On the west side of this axis 
of fracture and elevation, the rocks dip to the westward at variable, bat 
generally at sniall angles, while on the east side they dip at a high 
angle to the eastward, and are frequently vertical in their stratification." 
(p. G4.) Farther reference to Becraft's Mountain is made on page 1)0; 
it is also said that west of the line of fracture "the superincumbent 
rocks overlie this [Hudson slate] series conformably in most places." 
The several lleldcrberg outliers known to Matlier are Bccraft's Moun- 
tain and Mount Bob near Hudson; another in Grcenbush, between the 
Sandlakc and Nassau roads, about two miles from Albany, first examined 
by Dr. Eights ; and two others described by Eaton, one in the north 
part of Grcenbush, five miles southeast of Troy, the other in the town 
of Schaghticoke, on the north side of Tomhannock Creek (p. 87). 

The same. Geology of New York, First Distret, 1843. Most of 
the observations arc repeated from the Annual Reports, pp. 330-373. 
Bccraft's Mountain is described in detail (p. 351) and figured (PL 24, 
fig. G, here copied, fig. 7) : no doubt is expressed of the unconformity 
there ; but at Mount Bob (PL 38, fig. 1, here copied, fig. 8) it is said 
to be "apparent." "Although the actual junction of the roeks of 
the Hudson Kiver group with those of the Hclderberg division was 
not observed between Kingston and Catt^kill, they were seen in many 

.'■ PL 

■_^ r_ ^-- 

_v_ -I -:< J'*-^-»'"^X tMT j-i -r'l 



places so nearly m contact, and unconformable, as to leave scarcely a 
doubt that they were really unconformable" (p. 374); and they arc so 
shown in his section on Esopus Creek (PL 7, fig. 9, hero fig. 9) ; the 
author suggests that the Hudson sci'ies may have been disturbed first 
only to the east of the ''anticlinal axis," and, later, to the west with the 
overlying formations (p. 374). But his section (PL 38, fig. 14, hero 
fig. 10) at CatskOl shows conformity. 

H. D. Rogers. Second Annual Report on the Geological Exploration 
of the State of Pennsylvania. Plarrisburg, 1838. The sandstone and 
conglomerate of IV. (Oneida and Medina) are " displayed near Eondout, 
resting tinconformahlg and with a gentle inclination upon the steeply 
uptilted, contorted, and disrupted strata of the immediately subjacent 
slates" (p. 37). In Pennsylvania, the conglomerate at the base of IV. 
contains fragments of the three earlier formations, showing a violent 
pfiysical change; but no unconformity was noted there (p. 36). 

The same. On the Correlation of the North American and British 

Palaeozoic Strata. Brit. Assoc. Rep., 185G (178-180). *' Undulated 
Matinal rocks support horizontal Niagara or Scalent strata, with a lapse 
of two intermediate formations for some distance from the Hudson, 
westward along the base of the Helderbcrg range." (p. 178.) In the 
Mohawk vallev, these formations approach conformity. Southwcstward 

to Alabama there is neither lapse of formations nor unconfornuty, but 
a violent change in the rocks in passing from Hudson River to Medina 
strata ; the latter contain fragments of earlier formed layers. 

The same. Geology of Pennsylvania, 1858, II. (784-787). *' From 
Gaspe on the Gulf of St. Lawrence, S. W. to the River Hudson, wherever 
the Matinal rocks appear in contact with any of the superposed forma- 
tions, the former are cither highly inclined and folded, or give evidence 
of disturbance and partial metamorpliism, while the overlying strata 
display much less displacement and alteration." (p. 785.) Beeraft's 
Mountain and Rondout (fig. 11, here copied from Vol. II. p. 785) arc 
mentioned as points where the unconformity is distinct. It is said to 
exist "from Rondout to Selioharie" (p. 785). 

E. Emmons. Agriculture of New York. Albany, 1840, I. The sec- 
tions in the gorge of the Catskill at Austin's Mill and at Becraft's 
Mountain are drawn showing a conformable sequence of Waterlime on 
Hudson River layers (his sections 5, PI. XX. and p. 130, here figs. 12, 
13) ; at Rondout, the reljition is represented as unconformable by fault- 
ing (fig. 17, p. 134, here fig. 14). 

James Hall. Palaeontology of New York, Vol. II. Albany, 1852. 




"Along the base of tlic Heldcrberg, where the Chnton, Niagara, and 
Onondaga salt groups are very thin, the Oneida conglomerate is absent, 
and the shales and sandstones of the Hudson Eivcr group rise to within a 
few feet of the Tcntaculite limestone or Waterlime group." (p. 1, note.) 

The same. Palsuontology of New York, Vol. III. 1859. The author 
repeats a doubt previously expressed as to the truth-of the unconformity 
at Becraft's Mountain, and states that the Upper and Lower Silurians 
are conformable on the northern front of the Ilelderberg Mountains 
(p. 33, note). Farther on, he writes : "The Hudson Eivcr group, which 
constitutes a few feet of their [Catskill Mountains] elevation at the base, 
is disturbed, and the succeeding beds lie upon this unconformably " 
(p. GO); and again, "the unconformability of the Lower Heldcrberg 
group upon the Hudson lliver group" shows that the subsidence of the 
old sea bottom was periodical (p. 70 ; see also p. 88). 

These are the older observations on the subject. The following ref- 
erences show the recent work, as well as the lack of agreement on the 
question in the two text-books in more general use. 

J. Leconte. Elements of Geology. New York, 1878. " In the United 
States, the rocks of the whole [Paleozoic] system are conformable." 
(p. 277.) 

J. D. Dana. Manual of Geology. New York, 1880, The making of 
the Green Mountains came at the end of the Lower Silurian (211, 212) ; 
the disturbance extended to the Hudson (214). Localities of uncon- 
formity mentioned are near Gaspc, near Montreal, and at Becraft's 
Mountain (210,* 241), The disturbance is thought not to extend 
southwestward of New Jersey (217). 

J. G. Lindsey. A Study of the Eocks. Poughkeepsio Soc. Nat. Sci. 
Proe., II., 1879, 44-48, giving a careful description of the rocks at the 
Eondout cement quarries, and regarding the junction of the Upper and 
Lower Silurian rocks as unconformable. 

T. N. Dale. The Fault at Eondout. Amer. Jonrn. Sci., XVIIL, 
1879, 293-295, from which figure 15 is here copied, showing the Lower 
Ilclderbergs, with a thin layer of Niagara (Encrinal) limestone at the 
bottom, lying squarely across the tilted Hudson Eivcr strata. 

It would seem from this review that Mather and Eoircrs rejrardcd the 
contact of the Upper and Lower Silurians as unconformable on both 
sides of the Hudson ; Euunons iigures a conformable relation, and con- 
siders the apparent unconformity at Eondout the result of a fault; Hall 
at first admitted the general unconformity, but later doubts it even for 

* Ilcm Becraft'a Mountain is wrongly said to be west of the Hudson, 
VOL. vil. — i>o. 10, 21 



Becraft's Mountain (but not for Rondout 1). Leconte, on I know not 
Vhat authority, takes a view opposite from the generally accepted one 
given by Dana. Liudscy and Dale both represent the junction at 
Rondout as an unconformity. 

West of Catskill, I am persuaded that no unconformity exists : the 
evidence for this conclusion is given below. Becraft's Mountain and its 
smaller neighbor I have not seen, except from the railroad in passing : 
the opinions concerning this important point are contradictory, Mather 
and Rogers being opposed to Emmons and Hall, About Rondout no 
disagreement is directly expressed except by Emmons ; and yet none of 
the observations or figures of the hill-sections in that district are con- 
clusive; none enable the reader completely to exclude the possibility of 
the apparent unconformity being really a junction by faulting. It 
would seem, therefore, that all this subject needs reviewing. 

The observations on which I rely to prove the conformable sequence 
of the strata in the district hero mapped are as follows : — 

First. At the north end of French's Quarry Hill, by a good spring on 
the middle one of the tiirec roads that run around the slope, there is a 
contact of sandstone and an impure limestone clearly shown for some 
ten feet. The rocks here lie horizontal in the axis of a synclinal fold ; 
their strata are closely parallel, and evenly superimposed ; going down 
hill several outcrops of sandstone may be found ; ascending to the south, 
the several limestones of the Lower Helderbcrg group are easily recog- 
nized in proper order; going east or west, the Hudson River strata soon 
rise from the synclinal axis, becoming steeper and steeper by gradual 


Second. In the road and railroad cuts just east of Austin's Mill on 
the Catskill, the absolute contact is hidden by about ten foot of detritus, 
but the strata show only parallel arcs of the eastern half of a synclinal 
(see fig. 3). The apparent unconformity in the limestones here shown 
is due to horizontal faulting in the trough of the fold, as is described 
farther on. 

Third. Along the front bluff of the Kalk Berg, generally marked by 
vertical strata of Waterlimc and Lower Pentamerus, the sandstones are 
also vertical and parallel in strike; in the anticlinal valleys within the 
belt, the sandstone is perfectly conformable to the curves of the lime- 
stones, but no absolute contacts were found. 

Wo therefore must conclude that the entire series is conformable in 
this district, and is folded together; and so it is represented on our 



When the attempt is made to restore the geographic changes by which 
the several strata were made to vary, it cannot be denied that this con- 

formity is difficult to understand. The sands of the Hudson River group 
indicate a return of the shore line on the cast after the open ocean con- 
ditions of the Trenton formation ;* the shallowing of the waters and the 
westward advance of the shore continued certainly as far as the present 
line of the Hudson. If the unconformity at Bccraft's Mountain be ac- 
cepted, then we may follow the generally allowed belief in the folding of 
these sandstones accompanied by their elevation and erosion; and the 
very variable composition of the Niagara group as a whole, and the prob- 
able changes of level during the Onondaga (Salina) period are most likely' 
to be explained by the oscillations of the adjoining land on the east dur- 
ing the Green Mountain growth. Excepting the few feet of beds found at 
the northern end of the Quarry Hill, which were not definitely referred 
to any group, there is nothing to be seen in the Catskill section to repre- 
sent this vast lapse of time ; for directly and conformably above the Hud- 
son River sandstones come the Lower Helderberg limestones, which mark 
the second and greater eastward advance of the sea in the Upper Silurian, 
the first being that of the Niagara limestones. The present Catskill 
district cannot thou have been dry land, for it shows no eroded surface 
beneath the Lower Helderbergs so far as we could discover. It could 
hardly have been far under water, for then it should have received some 
share of the various sediments so plentifully supplied to the ocean far- 
ther west and southwest. It may, therefore, be best to suppose that our 
district lay just off shore, or almost between wind and water, and either 
received very little detritus, or else was alternately covered and swept 
bare again by shoal water currents, so that in the end it had gained 
scarcely any rock material. 

The change that followed next was not so much a deprcssLa of the 
ocean floor as a distant eastward retreat of the shore line ; for the Lower 
Helderberg limestones show shallow waters, witli freedom from shore 
sediments such as the Green Mountain rocks could have furnished. The 
Catskill shaly limestone probably marks a slight departure from this 
open ocean, and the presence of a neighboring shore, for it contains 

much more non-calcareous material than the limestones above and be- 
low it. 


This second oceanic cycle ends with the Oriskauy sandstone, marking 
a return of the shore, though perhaps not a very near approach; and 

* See Professor Newberry's "Circles of Deposition," &c. 
XXII., 1873, (2,) 185-196. 

Amer. Assoc. Proe., 




a third cycle culminates in the Corniferous limestone, with deeper water 
here than the second. The Marcellus shale, which follows abruptly, 


a change to shallow water or a neighboring shore ; the disappearance of 
the limestone below it was more probably connected with a further 
deepening of the water, or with a change in its temperature. But shal- 
low water and near shore conditions came very clearly in the cross-bedded 
Hamilton and higher sandstones, and even more distinctly in the Cat- 
skill conglomerates. 

It is difficult to say what is here meant by "shallow water," for we 
know too little of the winds and currents of these old times. But the 
meaning of *' near shore" can be estimated from the Catskill conglom- 
erates, the coarsest of the entire series here seen from the Hudson Kiver 
upwards, and therefore probably nearer their source than any of the 
other fragmental strata ; and yet the crystalline rocks from which their 
pebbles have been chiefly derived cannot be less distant than the High- 
lands of the Hudson (forty miles), the same series of rocks in Connecti- 
cut and Massachusetts (forty), or the Adirondacks (sixty miles), for all 
the intervening areas, even if then exposed to erosion, were of non- 
crystalline rocks. " Near shore " does not, therefore, necessarily imply a 
very close neighborhood to land ; and the carrying power of the paleozoic 
currents must have been very cohsiderable. The identification of the 
source of the Catskill conglomerate pebbles is an interesting and impor- 
tant piece of work. 

Folds and Faults. 

The folds of small radius and varying form into 
which the above-described strata have been pressed, and the strong in- 
fluence of the rocks' attitude on the surface form, combine to render this 
district an excellent training ground for Appalachian work. I know of 
no Other where so many structural problems are as well shown within so 
limited a space. Two well-known features are clearly seen : the folds 
become more pronounced in going eastward, and all the anticlinals have 
their steeper dips on the west. Points of special interest may be named 
as follows. 


The Catskill gorge from Austin*s Mill up to Leeds gives a very fine 
series of natural sections. The railroad cutting and the lane leading up 
from the mill to the turnpike give good evidence of the conformity of 
the Hudson Biver strata under the limestones, and the Wateriime here 
presents two interesting forms of distortion. The first is an unconform- 
ity by horizontal faulting (fig. 3) ; the layers have been shoved past one 
another on an oblique crack. ' It is worth noting that a similar style of 

n^^ f _ 


disloqation would probably be called true unconformity if it had taken 
place and been laid bare just at the junction of thia formation with the 
Hudson strata below it; but happening twenty feet higher, it can be 
referred to its true cause. Secondly, we may note the effect of internal 
disturbance in the limestone, shown by the breaking up of some of its 
fine layers (fig. 16) : this must be rcfori-ed to the epoch of general fold- 
ing, for examples can be found of all sizes up to a coarse brccciated mass 
several feet thick near the fault-unconformity ; it is therefore an example 
of what Heim calls folding with fractux'c, as distinguished from folding 
by bending; and is explained by him ae a folding that took'place under 
a pressure of superincumbent rocks insufficient to cause plasticity in the 
brittle strata.^ This fact may some day yield a measure of how many 
hundred or thousand feet of rock were not over the Waterhme when it 
was folded, and so lead to a conclusion respecting the former eastward 
extension of the Hamilton and Catskill sandstones. 

Another conclusion may be noted : the strata showing these crowded 
layers lie near the axis of a synclinal trough, where it is often stated 
that folding produces tension, not compression. Scrope, for instance, 
compares folded strata to a bent board, which of course is stretched on 
its convex side.f Such a comparison is incorrect. Kone of the deep- 
lying rocks can escape compression during their folding : this can 
happen only to the superficial strata of the anticlinals. "liai; synclinals 
are actually compressed, and not stretched, is shown by the growth of 
subordinate folds often found in their troughs ; by the cleavage of slaty 
rocks at such points; and in general by the thickening of (argillaceous) 
strata at the turns and the thinning at the shanks or tangents of the 
folds, as was long ago pointed out by Sir James Hall,| and lately 
confirmed by Heim.§ 

Across the stream from the mill is a well-formed synclinal outlier 
(see Emmons, PL IV.) capped with Lower Pentamerus and perhaps with 
some Catskill Shaly limestone. Farther up the gorge, where the stream 
turns to the rock-strike, there are excellent, exposures of Lower Pentam- 
erus on the eastern (left) bank,' and of Catskill Shaly opposite; the 
latter dips gently to the west at this point, but following it one third 
of a mile south, it becomes steeper, and at last is overthrown so as to 
dip 50° to the east. Above the next band, about at the middle of the 
west-east course of the stream, on the north bank, a distinct fault may 

* Meclianismus der GebirgsbiMinig, 1878, II. 31, 

t Volcanos, pp. 51, note, 289. 

X Edinb. Plul. Trans., VII., 1815, 97. § Loc cit- F. 48. 

■ L-X ^ LH-V ^aj T^^T 



be seen at the side of the railroad. The plane of the fault dips 45"" 

e^st; on the western side, the Upper Pentatncrua has a smooth, well- 
rubbed wall ; on the east, the Catskill Shaly ends more unevenly, and 
supplies a quantity of fragments for the two feet of fault-breccia. There 
is no noticeable contortion of strata on either side. This example is 
interesting as it m a violation of the so-called ''law of faults," (which I 
believe is no law at all,) for the upthrow overlies the hade. In this 
particular it confirms the hypothetical attitude of the fault-planes as 
generally drawn in Appalachian sections by Lesley and others, although 
these seldom if ever depend on* direct observation. The example is 
further of use in showhig that the fault may result from the same com- 
pressing force as the fold ; and not from horizontal tension, such as is 
needed for the so-called normal fault. The throw here on the bank is 
probably fifty or seventy feet ; it could be closely measured by more 
leisurely observation. We succeeded in finding the apparent continua- 
tion of the same fault half a mile to the north, but the intervening 
details of the map need revision. On the next turn of the stream by 
the railroad bridge, the upper limestones arc finely shown on the east 
bank; on, the other side, an obscure fold or fault complicates their 
succession. The grits and th(? thin Oriskany layer in the gorge at 
Leeds have already been mentioned. 

A cross-fault probably determined the gap on which the Kaatcrskill 
turns eastward from the Marccllus at the saw-mill ; for the folds do not 
correspond on the two sides of the gap, and the vertical limestones of 
West Berg seem displaced where they reappear on the north. 

Other points of interest are as follows, beginning at the north end of 
the map: — Black Lake and a high hill next west of it; the hill is a 
saddle of grits on a limestone anticlinal ; a rare occurrence. Canoe 
Pond and the steep plunge of the limestone under it^ eastern side. A 
Corniferous arch on either side of a little cross valley through which the 
railroad passes south of Leeds. The Quarry Hill synclinal and the 
Fuyk Valley anticlinal. The long tongue of Corniferous running down 
to Van Luven*s Lake, and the large loose blocks of limestone at several 


points along it. The southern anticlinal valley, and the narrow faulted 
grit synclinals to the east of it. The way in which the several lime- 
stones wrap around the disappearing ahticlinals is beautifully shown. 

Surface Geology. — Glaciated rock surfaces are very seldom seen 
within the Little Mountain belt, but this is merely because the rocks 
are generally too weak to hold them. The firmer sandstones of the 
Hudson River group to the east show them abundantly, as on a large 


■ *" - 



On tlie moutitaiu road a«coiidiiig to Beach's Mountaiu 

On the new road leading from the 

knob of rock alongside of the Mountain road in the village of Catskill 
just west of the stream; ita steep northern slope gives a good small 
example of an overhanging polished surface. The only case of glacial 
action noted on the limestones was on the vvestcrn side of the Cornifer- 
ous anticlinal, where the Kaaterskill has recently cut away the pro- 
tecting clays, just south of its cross valley by the saw-mill : these striso 
arc very well preserved ; they run horizontally along the steep lime- 
stone stratum, parallel to the valley. The Hamilton and Catskill sand- 
stones west of our limestone belt preserve many and distinct scratched 
surfaces : the largest of these was found on a bare even bed of rock on 
the Mountain road at a four-corners, abput half-way fi'om the MarccUus 
valley to the foot of the long grade ; they bear S. 20° W., and some 
are contimious for fifty feet. A little farther west the same direction 
is repeated, and with it there are many straggling scratches turning to 
S. 60° W. 

House, about half-way up its long grade, the scratches run S. 25° W., 
parallel to the mountain face. 
Kaaterskill Hotel eastward across the plateau to South Mountain, the 
freshly uncovered 'sandstone ledges show very distinct Stossseiteriy indi- 
cating an ice-overflow from the Hudson valley across the mountain and 
up the Palenville clove ; the directions of ice-motion, here clearly deter- 
mined by the form of rock-surface and the well preser\xd scratches, 
were IN'. 80^, 75°, 50°, and even only 35° W., giving a westward deflec- 
tion from the main valley of more than a quadrant.* 

The general absence of drift over the limestone belt and the sand- 
stones to the foot of the Catskills is noteworthy ; largely on this absence 
depends the clearness of the topography of the region. There are no 
sheets or mounds of till or gravel; everywhere but in the deeper valleys 
the country rock comes close to the surface and appears in abundant 
outcrops ; and the drift is recognized only in scattered stones and boul- 
ders of northern origin : in French's quarry there is, for example, a two- 
foot boulder of garnetiferous granite, presumably from the Adirondacks. 

There is no clear evidence of any marked elTect of glacial action on 
the topography, unless we place the little Black, Canoe, and Van Luven's 
lakes here ; but they are small, and probably very shallow, and quite 
as likely the result of drift obstruction as of ice excavation : they all 
occur on the lower part of the grits, where these join the Upper Pcntam- 

* This dcdcction lias been 
Journ. Geol. Soc, XV., 1859, 

observed by Mather, 
208 ; and Julien, N. 

1S43, 203; Eamsny, Qnnrt. 
Y. Acad. Sci. Trans., 1881. 



erus, and this as we know elsewhere shows a tendency to valley form. 
We had not time to study the origin of the basin of Green Lake, the 

laro;est of the district. 

The large blocks of Corniferous limestone, weathered loose along its 
margins, may be mentioned again here. The best examples are on the 
Old King's road where it joins the Mountain road ; several of the 
blocks are eight or ten feet cube. They cannot be considered simply as 
glacial boulders, for they occur only along the disappearing margins of 
their formation ; they cannot be of pre-glaciai weathering, for the ice 
stream that filled the Hudson valley till it overflowed its mountain 
boundaries east and west can hardly have left any loose blocks so near 
where it found them. So we are forced to consider tliem largely the 
product of post-glacial weathering, mostly by solution; but this gives a 
so much greater measure of post-glacial erosion than is generally found, 
that it is not satisfactory. Some of the blocks are separated from one 
another and from the still continuous bed out of which they seem to 
have weathered, by a hundred feet or more. The limestone would 
therefore have to be easily dissolved by surfiace waters, although it is 
very dense physically; and yet the same limestone under the clays of 
the Mareellus valley, where much water must have fdtered in along the 
contact of rock and clay, has not lost its glacial scratches. The case is 
not satisfactorily explained. 

All the lower valleys are occupied by stratified clays capped with 
sands up to about one hundred and fifty foot above the Hudson (tide- 
water). Near the river, the area and often the depth of these clays are 
very great ; they cover all but the higher sandstone ridges, which crop 
out as rocky islands. Farther back from the river, the clays fill the 
depressions among the limestones, as is nicely shown in the Fuyk, when 
viewed from the Lower Pentamerus cliff on the east; and the long 
valley cut on the Mareellus shale, where it is followed by the Kaatcrs- 
kill and far north and south as well, is deeply buried under the clay 


It is easy to see that,' if the clays were stripped off, and the country 
elevated several hundred feet as it has been in the past, its valleys and 
drainage would be considerably changed from their present arrangement ; 
but just what these changes would be is difficult to say. I think it 
probable, however, that the Kaaterskill would leave the Hamilton a 
little to one side of its present course at Big Falls; that both the Kaa- 
terskill and the Catskill would run along the Mareellus valley at a 
lower level than their present beds, and would escape eastward by some 

» « 



cliannel farther south than our map extends. If this view is correct, it 
follows that Big Falls, like so many other cascades in New York and 
other glaciated States, result from an old stream's taking a new course 
(L behevc this to be a general explanation for many falls) j that the 
Kaatorskill now makes its way through the Little Momitains over a 
broadly open pass that once led from the Hudson to the Marcellus 
valley ; that the Catskill, although larger than the Kaaterskill, was 
accidentally turned into a smaller cross-valley,, which it has since deep-^ 
ened somewhat into the appearance of a gorge. Such disturbance of 
pre-glacial drainage is a very common occurrence in oar Northern regions, 

and often gives rise to lakes. 

Further study is needed to learn the features of the Helderberg 
folds as they extend northward to the south line of Albany County, 
where Mather (1843, 335) says they end, and to show their increase 
to the south. 

Since writing my article for Appalachia, several months ago, an excur- 
sion to the mountains in Central Pennsylvania has given me new reason 
to repeat what was then said concerning the advantages of the Little 
Mountains for studying the elements of topography ; for in Pennsyh 
vauia the structural features are on so much vaster a scale, that days 
are there required for what can be seen much more cleai-ly in a few hours 
near Catskill. 

This article is accompanied by two plates, numbered XIL and XliL 

Plate XIL contains sixteen figures, described in the text. 

Plate XIII. is a colored map showing the district hero described. 

CAMBiiiDaE, January 15, 1883. 

- -- JT^Jt -X ^ urj> 4^^ — T7vn"-r^' 

-J- —^\'P^'rA 

^ill Museum Comp, ZooI.Voi;m.(GeoL5eTfe5l. 

HuosoN River Shales, 

f ' jli 

CATSKtLl. \ 



Fig. 2 

CoNTonrcD Hudson Rjv£.r Shales 


Fig 3 

TKt OrrsKiLL . 

Sccr/ow BELOW Austin's Mill 





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Fig. 6, 

F/G. 14 

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Ron pour, 

opp. WiLBOR, 


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Fig, 15 



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DIP 80.N/*0W. 



ElMMONS /846. 

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Ho 16. 





FROM Various Authors ^ original draw/ngs 

W M Davis 



The Hcliolype Printing 05.511 Tremont St .BoscOTi. 





August, 1S84. 


I , 





Synopsis oi^^ the Evidence on which the Rocks of the Azoic 
System have been vakiously gkoufed into Distinct Divisions 
BY American Geologists. 


The " MetJiTDorplilc Series" of Logan, as defined by Mm in tlie Report of 1845-46, 
331 ; his two divisions of the same, based only on theory, 332 ; his description 
^ of the Metamorphic Series on' the north shore of Lake Superior, in tlie Report of 
1846-47, 333 ; Hunt's subsequent niisreproseniaiion of Logan's views, 334. 
MuiiiiAY's description of the formations of the Kamanistiqnia Basin, 334 ; the 
two series of rocks subse(iuently known as the Laurentian and Huronian shown 
by him to be conformable, and to pass imperceptibly into each other, 334 ; this 
fact not mentioned by Hunt in his account of Murray's Report, 334. Murray's 
description of the rocks on the north shore of Lake Huron, Report of 1847-48, 
335. Louan's description of the same, in 1848, 335, 336 ; he confuses the 
Azoic rocks of Lake Huron with the Taheozoie of the south shore of Lake 
Superior, 330 ; Hou(;irroN'.s views misrepresented by Logan, 336. Murray, 
in U(!port for 1848-49, again d(\seribes region north of Lake Huron, 337. 
Logan, in 185-2, calls these rocks Cambrian, 337. In the Report for 1852-53, 
published in 1854, Logan gives the name "Laurentian" to the rocks pre- 
viously designated byhhu as *' Metamorphic " or Cambrian, this name being 
the e(piivalent of the term Azoic, previously introduced by Foster and Whit- 
ney, 337, 338 ; the term " Huronian" first used, by Hunt, in 1855, 338 ; the 
Huronian said Ity him to be unconformable with the Laurentian, 338 ; this an 
error, base.l on the eonfounding, by Logan, of the Azoic of- Lake Huron with 
the Paheozoic of Lake Superior," 338. First mention of the Huronian in the 
Canada, Rept)its, 338, 339. The relations of the Laurentian and Huronian indi- 
cated in R(^port for 1856, 339 ; relation of the hypersthene rock, since called 
*' Norian," indicated by Hunt, 1855, and again in 1856, 339. Division of the 
Azoic into Laurentian and Huronian, and the name Laurentian opposed, and 
Logan's entire misconception of the geology of Lake Huron and Lake Superior 
pointed out by Whitney, in 1857, 340; Logan recognizes his mistake, but 
does not abandon the terms introduced by him, 340 ; further statements of 
Logan (1857) in regard to the Laurentian and Huronian, 340, 341 ; peculiar 


= !^ 


1 ' 

E -^ 



^ I 
■ ^ 





logic of hh statements indicated, 341. Bigsby points out that the Huronian is 
distinct from the Cambrian and conformable with the Laurentian, 341, 342. 
Logan's statement, in the Report for 1863, that the Laurentian rocks had 
been shown by the Canada Survey to be mctamorithic sedimentary, controverted, 

342. The relation of position of the Lauj-entian and the Huronian discussed, 

343, 344. In the Report for 1863, Logan abandons the idea that tlie copper- 
bearing rocks of Lake Huron and those of the south shore of Lake Superior are 
of the same age, 344. Hunt's. views, set forth in the same R-eport, .as to the 
sedimentary character of the labradorite rocks in the Laurentian, 344. Maofau- 
LANE, in the R.eport for 18G3~66, describes the contact of some supposed 
Huronian with the Laurentian, on north shore of Lake Superior, near Miclii- 
picoten Island, 345 ; his observations show that both formations are eruptive, 
and of the same age, 346. Hunt, in Paris Exhibition Report of 1867, chiinis 
that the Laurentian comprises two distinct sets of rocks, unconformable with 
each other, 346. Richardson, in Report for 1866-69, on the Laurentian of the 
Lower St. Lawrence River, 346. Maiu;ou says that the Laurentian is a mix- 
ture of the Upper Taconic with the " Triassic of Lake Superior," 347. Bell, 
in the Reports for 1871-72 and 1872-73, points out the conformability of the 
Huronian and Laurentian in the region northwest of Lake Superior, 347, 348 ; 
Selwyn thinks this apparent conformity only local, and that, there is really a 
very considerable break between the two formations, 348. Sjclwyn's views 
shown to have no basis of fact, 348. G. M. Dawson's and Bell's observations 
in the same region, 349 ; their views criticised arid commented on, 349. 'Bkll, 
in the Report for 1877-78, shows that the Laurentian and Huronian are con- 
formable in the Hudson's Bay region, 349, 350. 

First . mention of the Hastings series, by Muuuay, in Report of 1852-53, 350; 
the same discussed by Macfaulane, in Report of 1866, also by Logan, who 
says that it is conformnble with the Laurentian, 350 ; Hunt says that the 
Hastings scries is overlain unconformably by the Upper Laurentian, 350. 
Vennoi'. gives two entirely different sections of the Hastings series in 1867, 
and in the Report for 1866-69, 351 ; his views as to the relations of this series to 
the Laurentian and Huronian, 352-354. Hunt, in 1869, refers ihc Hastings 
series to the Laurentian, 350 ; in 1870, to tlte Terranovan, this ludng. regarded 
as in part Potsdam, 354, 355 ; Hunt, in 1871, says that the Hastings series is 
conformable with tiie Laurentian, 355 ; later in the same year, that it is not, 
355 ; in 1875, he says that the Montalban or Hastings series occupies a position 
between the Laurentian and the Trenton, 356; in 1878, he refers the Hastings 
series to the Lower Taconic, and misstates the views of Logan and Bell in 
regard to its conformability with the Laurentian, 356. Selwyn announces V(;ry 
dilfercnt views from those of Hunt, and shows up something of the prevail- 
ing confusion in Canadian geology, 356-359. Macfaiilane, 1879, objects to 
Selwyn's views, 359 ; J. W. Dawson asserts his disbelief in tlie results of the 
Canada Survey, as bearing on the age of the Hastings series, 359. 


J. W. Dawson, in 1855, refers the rocks in the vicinity of St. John to the Lower 
Carboniferous, and in 1861 to the Devonian, 360 ; Matthew divides the same 



rocks into six groups, and refers to Devonian, Stlurian, Laureutian, and ITu- 
ronian, 360-362. Bailkv, Mattiikw, and Haiitt, in 1805, give their views 
of tlie age of the roclcs of SoaUieru Now Brunswick, 362, 363. Bailey and 
Matthew again, in the Report for 1870-71, express tlieir opinions of the 
sequence of these roclis, 364 ; numerous clianges made, to conform witli the 
views of Hunt based on lithological considerations, 364 ; confusion thus intro- 
duced, 364-366 ; faults and overturns imagined in order to sustain these new 
views, 367 ; an easy explanation of the dillieulties, 367. Further confusion and 
sliifting of the various groups fronx place to place by Mattilew and Bailey, in 
the Reports for 1876-77 and 1876-78. Ells, in the Report for 1876-78, 
describes rocks as Laurentian and Devonian, which in 1865 were called Devo- 
nian, and in 1871 Ilurouian. Further changes, and the St. John group placed 
in the Cambrian, in the Report of 1878-79, by Matthew, Bailey, and Ells, 
368. Bailey's view of New Brunswick geology, in 1880, 368, 369. Hunt, in 
1878, pr(isents his views of New Brunswick geology, mingling his own ideas witli 
those of Bailey and Matthew, and disregarding the se<picnce of time in which 
these were presented, 371 ; resulting confusion, 371 ; impossihility of har- 
monizing Hunt's views, as expressed in 1870, Avith his subsiMj^uent explanation 
of them, 372 ; a tabular statement of Hunt's views as expressed by him in 1870, 
and as that expression was explained by him afterwards, 372 ; remarks on the 
value of the work thus done, 372. Matthew and Bailey misrepresented by 
Hunt in 1879, 373. The rocks of Southern Kew Brunswick declared by Hunt, 
in 1875, to be Huronian and Montalban, 373. Various views of the New 
Brunswick geologists, so far as the same can be deciphered, presented in tahular 
form, 374. 


Hind, in 1870, indicates the presence of Huronian and Laurentian in Nova Scotia, 
374, 375 ; J. W. Dawson regards the Laurentian gneiss of Hind as being 
intrusive granite, 375 ; Selwyn differs from Dawson, 375 ; Selwyn's views 
ciiticised, 375 ; Hunt considers the Iluroiiiau of Hind to be Montalban, 376 ; 
Honeyman's views, which seem to be valueless, and are objected to by J. W. 
Dawson, 376 ; Hartley's opinions of rocks of Cape Breton, and some sugges- 
tions in regard to them, 376 ; Robb's examination of the same region, in the 
Reports for 1873-74 and 1874-75, 376; Selwyn's commentaries on Robh's 
work, 377; great change in Sklavyn's views since 1871, 377. Further stnte- 
ments by J. W. Dawson, in 1878, 377. The condition of the question summed 
up, 378. 


Reconnaissance by Juices, in 1839-40, 378. Murray, in the Report for 1864, 
recognizes the Laurentian, and gives a table of the formation occurring in New- 
foundland, 379. Hi the Report for 1868, Muuray introduces an Intermediate 
system, supposed to be the e(piivalcnt of the Cambrian and Huronian, 379 ; 
supposed fossils in this series, 379 ; these I'ejected by the palceontologist of the 
Survey, 379 ; further discoveries of supposed fossils in these rocks, 380 ; Mur- 
ray, in the Report for 1873, presents reasons for dividnig the Laurentian into 
. two groups, 330 ; the real state of the case, 380, 




Packaud's observations in 1865 ; he recognizes there, on very inadcr[uato evidence, 
tlie I^aurentian and LIuroniaii, 381 ; labradorite rocks seen, apparently eruptive, 
but called by him Norian, 381 ; JIind refers the rocks of Labrador to tho Lau- 
rentian on lithological grounds, 381 ; AViLKiNS holds the same views, calling a 
dike Norian, 382. 


Geological Survey nnder C. II. Hitciioock developed nothing of vahic in regard to 
the Azoic rocks, 382 ; Hunt infers that the mica schists and gneisses of Maine 
are of Montalban age, and that the rocks near Portland are Huronian, and older 
than the gneisses, 382 ; C. 11. IIitchoock holds exactly the opposite view, 
382; 1:^0 evid(mce whatever in regard to the age of the crystalline rocks in Maine 
other than lithological, 383. 


Hunt, in 1847-48, in 1863, and again in 1867, refers the rocks of the White Moun- 
tains to the Devonian, 384 ; Lesley does the same, and claims for the range a 
synclinal structure, 384 ; hi** probable error, 384 ; Hunt, in 1878, says that 
Logan consid(!red the "White Mountains as Devonian, omitting to state the fact 
that he himself had repeatedly published the same opinion, 384 ; Hunt, in 1870, 
called tlie White Mountains Terranovan, which he considered as being in part of 
Potsdam age, 384. C. IT. Hitchcock's first scheme of the rocks of New Hamp- 
shire, in the Report of 1869, in which most of tliem are referred to the Quebec 
group, 385 ; another arrangement, in the Second Report, for 1870, 385, 386 ; in 
the Third Report, 1870, the White Mountains are called Eozoic, which " satis- 
ftietory reference" is said to "clear up the obscurities of Kew Hampshire 
geology," 386 ; further changes, in Report for 1871, and introduction of the 
Norian, "the prevalent opinion in regard to tlie ag(; of the New England meta- 
morpliic rocks must be changed to conform to the discoveiy of labradorite in our 
State," 387 ; Hawses, however, regards the labradorite rock as eruptive, 387 ; 
Hunt, in 1873, accepts the Norian ; but, in 1878, says that it is found to be of 
eruptive origin, 388 ; C. 11. Hitchcock, in 1872, endeavors to prove that the 
Norian rocks are of sedimentary origin, 388 ; further remarks to the same effect 
by C. H. Hitchcock, in various papers published in 1871-72, 389 j also, in 
Final Report, Vol. II., in which we are told that " the facts as in.terpreted [in 
reference to the Norian or Labrador system] are of great consequence, since they 
fix the geological horizon of the whole Atlantic system," 389, 390 ; later on in 
the same volume, all that had been said of the Labrador system taken back, 
the roclcs recognized as being eruptive, and the exposures on Mt. Washington 
formerly considered as stratified now called "injected dykes," 390. C. H. 
Hitchcock, in tlie Report for 1872, assigns the Quebec group to the Huronian, 
the Concord granite said to be sedimentary,-' 391 ; the same author presents, 
in the Report for 1872, a classification of^the rocks of New Hampshire (see 
■Table), 391, 392; "granite flowed over the country like water," 392; "ten- 
distinct periods traced on the scarred sides of the White Mountains," 392 ; 



C. II. Hitchcock denionsUutes tlie iinport;mce of mineral characters in the 

classiiicatiou and idcntifKiation of rocks, 393; the rocks of New Hampshire 
classiiied on that basis, 393; Hunt caUed on by C. 11. Ilitclu^ock to decide 
which way the porphyritic gneisses dip, 394 ; Huntington points out facts 
indicating that the Concord granite is intrusiye, 394; C. H. Hitchcock states 
his views in Final Report, Vol. 11., in regard to tlte importiince of not "obscur- 
ing observations" by "individual speculations," 394, 395; sonic results of 
investigations made to ascertain how for 0. H. Hitchcock was able to distin- 
guish and prop(n-ly name rocks, 395-397 ; authenticity of siiecimeus examined 
by us, 397 ; notii^e of our tabular view of the elassitications presented at various 
times by the New Hampshire Survey, under 0. H. Hitchcock, 397, 393. 


S. Godon's observations in 1807-8, 398 ; his division of the formations in the 
vicinity of Boston, 398-400 ; Ma(U,uiie'.s geological map, 400 ; error of Hunt 
in describing iVlaclure's work, 400 ; J. F. and S. L. Dana's coutribirtion to the 
geology and mineralogy of the region near Boston (1818), 401, 402; Eaton's 
Index to the Geology of llic Northern States, 402; Thomas Cooper, 1822, 
recogniz(!s the volcanic character of some of the rocks near Boston, 403 ; Hitch- 
cock's first pubiieation (1824) in regard to geology of Eastern Massacliusetts, 
403 ; Hitchcock contributes to the geology of the same region in Eaton's Survey 
of the Erie Canal, 403, 404. J. W. Weuster, 1824-25, publishes Remarks on 
the Geology of Boston and its Vicinity, 404. HrrcHcocK's Report, 1833, and 
his tluioretical views as set forth in that volume, 405-409 ; his final report, 
1811, 409, 410 ; his theories sot forth and commented on, 410. Puescott's 
geological investigations in Essex County 839), 410. 

Hunt, iu 1854, refers the limestones of Eastern Ma.ssaehu setts to the Devonian, 411 ; 
he states, iu 1801, that he recogni;;es in New England or Southeastern Canada 
"nothing lower than the Silurian," 411. Discovery of fossils near Boston, and 
recognition of the locality from whicli they eanie, 411 ; various statements as to 
the dip of the rocks from whii'h these fossils came, 411, 412 ; Hunt, in 18(16, 
on the limestones of Eastern Massachusetts, considering it doubtful whether 
they may not be Laurentiau, 412 ; C. II. Hitchcock, 1867, considers the gneiss 
and hornblende schist of Andover to "belong to the Eozoic ages," 412 ; his 
rep(n-ted facts doubted, 412. Hunt, in 1869, describes the granite of New Eng- 
land as being a sedimentary rock, and containing traces of fossils ; in 1870 he 
say,^ that the granites of Cape Ann and Qnuicy are " probably intrusive " ; in 
1873, that tlie granites of Rockport are "distinctly eruptive," 413 ; neeossary 
pliysical conditions resulting from Hunt's theories, 413; Bickmkll finds 
Kozoon in liinestiinc at Newbiuy, 413, 414 ; Hunt considers this proof of the 
Laurentiau ago of these rocks, 414. 

SuALi'Ui, in 1869, considers the stratified origin of the syenites of Eastern Massachu- 
setts clearly proved, — the syenite being seen to pass into " uncpestionably 
sedmientary rock," 414 ; Ids geological observations sliown to be incorrect, 414. 
Hunt, in 1870, <'onsiders the finding of the Eozoon at Chelmsford, and its 
identification by Dawsou, as proof of the Laurentian age of the limestones of that 
region, 415 ; Hunt, in 1870, refers the gneiss of Eastern Massachusetts to tlm 

* t » 



Laurentian, and tlto dioritcs and porphyries to the Cambrian, wliich lie then 
considered the c(pnvalent of the lluronian, 416 ; he also says that tlie presence 
of the, Eozoon "can no longer serve to identify the Laurentian system, 416; 
Hunt, in 1870, further discasscs tlie geology of Eastern Massachn setts, 416, 
417 ; comments on the views there expressed, 417, 418. C. II. IIITOIICOCK, in 
1871, publishes a geological description of Massachusetts, 418 ; some of his 
errors pointed out, 418. Hunt, 1871, refers the felsites of Eastern Massachu- 
setts to the " great Iluronian system," 418. 

Hyatt, in 1871, considers the porphyries of Lynn and vicinity to be metamorphic 
sedimentary rocks, 418, 419; Hunt, in 1871, takes a similar view, referring 
these porphyries to the Huronian, and "the limestones, with Eozoon from East- 
ern Massachusetts," to the Laurentian, 419 ;, some comments on Hunt's method 
of misrepresenting statements previously made by himself, 419, 420 ; Hunt 
ao-ain, in 1871, holds that the gneisses and limestones of Eastern Massachusetts 
are Laurentian, 420. Hodge's classification of the rocks near Boston, 420, 421. 
Bouvit, in 1876, considers the felsites to ))e derived Jrom the metamorphosis of 
the conglomerates, 422 ; these views supported by Hyatt, 422, 423. Crosby, 
in 1876, divides the " Eozoic rocks " of Massachusetts into Norian, Huronian, 
and Mont Alban, considering these divisions *' as both lithological and chrono- 
logical," 423 ; the same statement affirmed in 1880, 423, 424 ; extraordinary 
nature of the views here advocated, 424 ; errors in Crosby's determinations of 
the rocks, 424. Crosby maintains that granites are derived from sedimentary 
rocks, 424 ; his mistakes as to the real chai-acter of the Rockport granite, 425 ; 
he considers tlie felsites near Boston to be of sedimentary origin, 426, 427 ; his 
ideas in regard to the Huronian, 427 ; in regard to the argillite aiid conglomerate 
near Boston, 428. Wadswouth's investigations, in 1877, of the dikes near 
Boston, 428 ; in 1878, of the Rockport granite, 428. Crosby, in 1879, advo- 
cates the theory that the felsites are of deep-sea origin, or made of the red clay 
deposited at the bottom of the ocean, 428, 429. WadswOKTH studies, in 1878-79, 
these felsites, in the held and microscopically, and makes them out to be old 
lavas, 429 ; the felsites seen by him in the form of dikes, 429. Dilleb, in 1880, 
makes an exhaustive investigation of the felsites north of Boston, and confirms 
in all respects Wadsworth's views, 430, 431 ; his held of work and collcctioiis 
carefully examined by the authors of the present paper, and the accuracy of his 
results testified to, 431. Ckosby, in 1880, designates wliat he previously had 
called .ne " Norian " as the ''Naugus Head series" ; this he considers the real 
base of the geological column in Massachusetts, 431, 432 ; Wadswobi-u Ihids Uie 
Naugus Head series to be of similar character to the zircon syenite of Norway ; 
CiiosBY's views shown to be incorrect, 432, 433. Cbosby's ideas in regard to 
the Huronian in Eastern Massachusetts, 433-435; his views criticised, and bis 
reported facts shown to have, in many instances, no other basis than his own 
inability to distinguish between dilferent rocks, 436. 

SllALFJi, in 1879, maintains that the shales and conglomerates of Roxbury pass into 
the'amygdaloidal melaphyr, 437 ; his theoretical deductions, made in accordance 
with this view, 437 ; Bknton, in 1880, controverts these views, and shows that 
the melaphyr is an old, altered basalt, 437. Discussion in regard to tlie plas- 
ticity of the pebbles in the conglomerate, 437, 438 ; opposite views of Ckosby 
and Wadswobth, 438 ; the spindle-shape, into which Ceosby thought that the 

At ^1 =^. 



pebbles had been squeezed or pulled, shown to be only the result of his mis- 
takirig the enclosing matrix lor the pebbles, 438. Dodge, in ISSl, gives 
details of his observations near L^oston, nofcieing the oecurreuee of felsite dikes in 
the granite, as had been before shown by Wadswortli and Diller, 439. Wads- 
WORTli, in 1881, calls attention to more of Crosby s errors of observation, 439. 
Wadswoiitji, in 1883, points out the relations of tho Roxbnry conglomerate to 
the argillite, 439. DoDUR, in 1883, claims that tlierc are two granites in the 
Quincy district, but olf(!rs no evidence in supjiort of this view, 439, 440. 
Errors of SuALioji, Uugeuh, and Jaokhon, in regard to the argillite and granite 
pointed out by Wadsworth, 440. 


Small progress made by the eai-lier invcsligaiors tow;ird 'unravelling the intricate 
problems presented in tliis region, 440 ; a specimen from Hitcikmick's Final Re- 
port, 440, H. D. Ro(JEn.s'K division of the rocks b(dow the " Cambrian or Older 
Silurian " into azoic and liypozoic, 440, 441 ; this elassiiication has no basis of 
fact, 441 ; he says that it is absolutely impossible to determine " the true base of 
the RaliEozoie system," 441. Importance to New England that the work of the 
Canada Survey shonhl be well done, 4.11. First publisljcd statement of the bear- 
ing of the results of that survey on the solution of problems in New England 
geology, by Hunt, in 1849, 441, 442 ; the whole of the Green Mountain rocks 
said by him, to belong to the Hudson River group, 441, 442. " Witli such a key 
to the structure of tho metamorphic rocks of New England, and of the n-,-cat 
Appalachian chain," Hunt thinks that "the diffiimlties that have long environed 
tho subject are in a great degree removed, 442; similar views expressed by 
Hunt, in 1850, and EmM(>ns> views of the age of the Tacouic entirely rejected, 
442 ; again, in 1854, Hunt refers the crystalline limestones of New England and 
their continuation southwest to the Lower Silurian, 412, 413; in 18()1 and 
again in 1863, similar views were expressed, 413 ; ui ISCiO, Hunt said that the 
Quebec group '' constiiuted the groat metalUrerous r(\giou of Eastern Canada, 
Vermont, and Newfoundhunl " ; he also refers the (niprifcrous rocks of Lake 
Superior to the same group, 443 ; in 18()7, ho repeated the same statement, eon- 
sideri]ig the Quebec group as being the equivalent o\' the Landeilo, and furilier 
remarking that this group formed the Notre Dame and Civcn Mountains, and 
that it " played a very important r6ie throughout tho Aitpalachiau chain," 443 ; 
this all repeat(Hl agahi later in the same y<'ar, 444 ; the statement also repeated 
that the White Mountains Avero of Devonian age, 444; again, in 1808, it is 
asserted that there is no proof of the existence in Vermont of any strata older 
than Potsdam, the gneiss of the Green J\Iountains being referred to the uin>er 
portion of the Quebec group, 444; oneo more, in 1870, HrNT assorts the lower 
Silurian a<j;e of tho Green ]\rountains, 445. 
In 1870, Hunt's views undergo nnaamorphism, and he claims that the theories 
which he liad ad vo('ating since 1803 were only liis ofiicial ones, and that 
his own views wore quite diiT^-rent, 445 ; the rocks of the Green Mountains 
begin to be eabcd Iluronian, tho idea of the Devonian ago of the Wliite Ab)un- 
tains being abandoned, and tho provisional name of Terranovan introduced for 
thorn, 440, 447 ; Dana objects to Ihose views for various reasons, and especially 
on the gi'ound thai minerals are not fossils, and that thoro is no reason for 




assuming a ohronobgictil order in minerals, 448 ; in replying to Daka, Hunt 
assorts that lie did not sav that the AVhite Mountain roclvs wore newer th;i.u 
those of the Green Mountains, 449 ; it is shown, however, that he had said this, 
450, 451 ; a comparison of Hunt's statements of what ho said witli wljat he 
really did say, 452 ; Hunt's methods set forth, 453 ; Dana's eoinnii'iits on 
some of Hunt's statements, 453, 454, 455. Dana remarks that Hunt's volume 
"contains a series of misrepresentations of the views of others wholly unueeessary 
and dillieult to find excuse for," 454 ; Dana's examination of the Helderberg 
rocks in the Connectieut Valley, with reference to the (question whether th(i age 
of strata can be determined by means of the minerals they contain, 454, 455; 
" lithological evidence worso than worthless," 455. Selwyn's opinion of the 
revolution in Hunt's views, 455 ; metamorplusm and mhieralization no test of 
geological age, 455. LKSLr.Y, in 1875, states that in Pennsylvania the Huronian 
or Green Mountain system overlies thu AVhite Mountain series, both being ohler 
than the Totsdam, 455 ; Dana's criLicdsm of Lesley's statements, 456 ; Lesij^v, 
in 1878, withdraws this opinion, and now considers that tiie Green Mountains 
are Pahcozoic and the Wlutc M.ountains Devonian, 456. Dana (1877, 1879) 
gives the results of his own and Wing's investigations in Vermont and W(.'ateru 
M^assachusetts, 456, 457 ; according to these, the Hmestones of tluit region are 
wholly Lower Silurian, and the Taeonic slates overlie them, and are of the nge 
of the Hudson lUver grou]), 457. Hunt, in 1878, further develoi)s his views 
in r(!gard to the Upper and Lower Taconie series, 457, 458. Hunt, in 1879, 
jives tlie reasons why he formerly referred the Green Mountain rocks to the 
Quebec group, when he in fact regarded them as Hurouian, 458; " ofheiid 
r(!asons " not oidy prevented his dissc-l^ng from Logan's vi(!ws, but caused him 
to afTirm tlieir correctness in the strongest possible manner, 458'; further light 
on Hunt's meUiods, 458. Various contradictory statements of C. 11. Hitch- 
cock in regard to Vermont geology, 460, 461 ; in 1877 Im considers the Green 
and the AA^hite Mountains *' nearer the Laurentiiut tiian the Huronian," iind in 
1875 thinks that Emmons understood the relations of the rocks called by him 
Ta(;onic "better than most of his contemporaries," 460, 461 ; in 1880 lu; finds 
that he had been in accord with Dana and Wing for years in their "disbelief in 
'Taconism,' " 400. In 1880 and 1881, Dana brings together the evidence in 
regard to the geological age of the Green Mountain limestones and associated 
rocks, showing beyond possibility of doubt that they are Lower SUurian, 
4G1, 462. 


Geology of the Adirondacks, 462, 463 ; Hall and Logan's views in 1864, 463. 
Discovery of I'x)zobn iu Westchester County, 463. Hall on the relations of the 
limestones of Northern New York, 463, 464. Lkeds, in 1877, on the lithology 
of tlie Adirondacks, 464 ; his views criticised, 464. Diutton on the geology of 
Richmond County, 464 ; insufficiency of his data, 465. 



IL D. Rogers's views of the age of the gneiss and limestone of this State, 465. 
Cook on the Azoic rocks, 465, 466; some suggestions in regard, to points 
needing further examination, 466 ; origin of the iron ores, 466. 




Views of IL D. Rogers in r(;gavd to tlio oldc;r rocks of this State, 4G7, 4G8 ; 
romarkablo contradictions in his statements, 407, 468. LIuNT employed by 
Lesley " to C))liate all the known, supposed, and suspected facts of American 
Azoic Geology," 408; result of the same, 409. Hunt's views, in 1801 and 
1871, of Pennsylvania geolog}^, 409, 470 ; here again most remarkable contra- 
dictions, 470. LIUNT, in 1870, makes various statements contradictory of Les- 
ley's opinions, 471. PiUME on the gneissic rocks of Lehigh County, 471 ; he 
contradicts Hunt in reference to the age of certain iron ores, 472. C. E. Hall 
ori the formations of Eastern Pennsylvania, 472. His results differ much from 
those of Hunt, 473. Some remarks of l^i^sLiiiY in regard to the remarkable 
diirerences between the views of J'kOGEiis and C. E. Hall, 473 ; a key to the 
geology found, but "it will not turn in the lock," 474. 


Fontaine's views of the geology ol' the vicinity of PalcoBy Falls, 474. Campbell 

on the samcs rocks, 475 ; his peculiar views iu regard to the Laurcntian and 
Huronian, 475 ; criticism of these views, 470. 


Keru's report of 1S75, 470, 477 ; he assigns a large portion of the State to the 
Laurentia.n and Huronian, 470, 477 ; Luadley, in 1875, considers a large part 
of these rocks as being Silurian or newer, 478 ; Kerr admits doubt in regard to 
the validity of his results, 478. No satisfactory reference of any of the rocks of 
this State older than the Trias, 479. 


Lieber's work gives no clue to the age or order of succession of the older cr^^stalUne 
rocks of this StaU;, 479 ; Hunt, however, from Lieber's description, considers 
that he identiiies the Oreen and White Mountain series, 4?9 ; Hunt's inferences, 
so far as can be made out, in contradiction with the sLatemouls of Licber, 480. 


Littll: says that there is no Azoic in this State, 480 ; Hunt, on lithological grounds, 
refers some of the rocks to the J\lontaIban, and some to the Taeonian, 480. 


Buckley's reports noticed and criticised, 480, 481 ; they are of no importance, 481. 


Safford on the older rocks of this State, which he sees no reason for referring to 
the Laurcntian or Huronian, 481. P>rai)LEY holds that all the metamorphic 
rocks of Tennessee are of Silurian age, 481. 

i-. . 





Owen'k views in regard to the crystalline rocky of this State ; ho holds that they are 

eruptive, 482. 


Nothing definite known in regard to the crystalline rocks of this State, except that 
most, if not ail, of them are eruptive, 482 ; they have heen assigned to the 
lluronian and Laurcntian on lithological grounds solely, 482. 


Koference to work recently published hy AVaj^sworth in regard to the geology of 
this region, '182. Ago of tlic cupriferous rocks of Lake Superior discussed, 
482-494; evidence ohtahied on hraiK'h of Torch lUver, 482-485; nature of 
these rocks indicated, 483 ; the facts discussed, 484 ; conclusions reaclu;d, 485. 
IiiviNo, in 1873-74, on the relations of the Lake Superior rocks, 485, 48t5 ; 
he adopts a diirerent theory, in part, in 1879, 48G ; Swkkt states facts in o])po- 
sition to the views of Irving, 48G ; our explanation of the phenomena, 487. 
luviNG finds evidence in support of his views at the Dalles, 487 ; Ciiamiseiilin 
holds the same opinion of this locality, 488. Selwyn, in 1882, states his views 
as to the age and I'clations of the Lake Su2)erior rocks, which he had previously 
called iJuronian, 488; these views identical with those of Fostek and W hit - 
KEY, puhlishcd in 1850, 488. InviNG replies to Selwyu, 489; Wadswortii 
replies to Irving, 489. IIt:nt, in 1883, states that Logan, in 1863, i)ut forth 
conclusive evidence that the cupriferous rocks of Lake Superior underlaid, un- 
confoi'mably, Ihc Potsdam sandstone, 489 ; Wadswoutii points out that Logan 
brought no such e\'ide]iee, 489. N. IL Wincuell agrees with Foster and 
"Whitney, and with Selwyn, 480. Chambehlin sums up his reasons for sup- 
posing the Keweenaw rocks distinct from the adjacent sandstones, 489, 490 ; the 
errors in his reasoning i)oiuted out, 490. Msu'int of the facts at the Taylor's 
Falls locality, 490 ; assumptions of the Wisconsin geologists, 490 ; what Owen 
Siuv tlu're in 1850, 490, 491. Observations of Kloos, iu Report for 1881, 491. 
N. 11. WlNCUELL thinks the sandstone at this locality more recent than the 
Potsdam, 491. Errors faPen into byluviNG and CiiAMliiouLiN poiut(Ml out, 
491. The so-called "Kcwcenawan Scrips" owes its origi?i to incorrect observa- 
tions, and ttroucous deductions, 491, 492; N. II. AVinciiell, in 1881, gives a 
sumniary of the opinions held regarding the copper-bearing rocks, made up from 
one ]U-eviously p\iblish(^d by Wadsworth, 492. AVadswokth iK)Uits out the 
ignuriuice of the primdplcs of geology and litliology displayed by Bj-ooks and 
Pumixdly, 492 ; they boiTow largely irom FosTKii and Wjjitnjcy's nia,p without 
giving any credil, 492. Romixoek on the A/oic ]-ocks of Micldgan, 492, 493 ; 
his views in regard to the eruptive chai'acter of the granites, 493 ; liis ]>rp.u]iar 
thc.ori<is of tlu; eruptive rocks, 493, 494 ; his observations iu the Menoniineo 
region, 494. Discussion of the origin ol' tiio iron ores in a previous publication, 
by WAnswouTiJ, referred to, 494. The views nuuntnined by Fosteii and Whit- 
ney, find by Wadhwoutii, sutttaiucd'by Selwyn, 494 ; these views opjjosed by 
DaiNA, 494 ; his reasoning criticised, 494 ; N ewijejiuy also expresses his opinion 




» « « 


on the subject, 495 ; Julikn does Liu; saiiu;, 495 ; bolli these writers show by 
their writings tliat tliey have inadii no investigation of the faets, 495. Swket^ 
in 1876, on a HUi)])osed niiconforniabilily of the Huronian and Laurentiaii at 
Penokoc Gap, 495, 496 ; luViNG on the same, 496 ; nature of such occurrences 
not understood by the Wiscou.siu geologists, 496. IiiviNO on the lluronia.u in 
"Wisconsin, 497 ; his ignorance of the necessary results of the intrusion of an 
eruptive into a sedimentary cue, 497 ; Irving adopts some of Wadsworth's 
lithoh)gical views, but omits to state the source from which thev were derived, 
497, 498. Hall, in 1866, refers the gneiss and granite of Redwood liiver to 
the Laureiitian, and some quartzites in Minnesota to the lluronian, 498 ; 
Hall's views opposed by IIaylln and N. H. Winoiiell. The cupriferous 
roelcs on Lake Superior, within tiic limits of Minnesota, referred to the Potsdara, 
in 1880, by N. H. Winciiell, 498. 


AVhat rocks are included in the " Archrean" by the Fortieth Parallel geologists, 499, 
500. The Azoic or Arch^v-an rocks of the Laramie Range, 500; Zirkel's 
distinctive characters of eruptive and scdimciitary granites, 500, 501 ; defect of 
las methods, 501 ; King's and A. llACiUE's statements at variance with eaeli 
other, 501. The Medicine Bow Range referred to the Huronian by A. Hague, 
602 ;*no proof given that it is ohhir than Tertiary, 502; defects of observation, 
502. The Uinta Range, 503. The Wahsatch Range, gradual change of views 
in regard to its age, as volume succeeded volume, 503-507- Conllieting state- 
ments of ZiRKEL and King, 507, 508. Criticism of KiX(;'s statements, and of 
his manner of observing, 508 ; similar criticisms by Geikie, 509, 510. Sum- 
ming up of tlu; results of the Eortieth Parallel Survey, and indication of their 
value, 510, 511. 


The rocks of the Chugwater, in 1868, called Laurentian, but no reasons given for this, 

511, 512 ; IIayden, in 18(59, states his theoretic views in regard to igneous and 
metamorphic rocks, 512. Haydkn caRs the rocks on tlie north side of the Uinta 
Range Silurian and Huronian, 512; tlie Fortieth Parallel Survey calls them 
Carbonifenms, Powell Devonian, iMinuons Cambrian, and Marsh Silurian, 

512, 513. Endlkui, in 1871, calls all the crystaRinc rocks in the region studied 
by him, at th'.; head of the Rio Grande and Rio Animas, Metamorphic PaliBozoic, 
613. Statement of Peale in, regard to crystalline rocks, 513. ENDLrciI divides 
the Azoic rocks into three systems, 613, 514 ; he admits the insufficiency of his 
observations, 514. Remarks by St. John and Pkalk, 514. Summing Up of the 
condition of things in the Rocky Mountains, 514, 515. 


No evidence offered in regard to the Azoic, 515. Stevenson in regard to age of rocks 
caRed Archaean, in parts of New JMcxico and Colorado, 515. 

1-— d —v^ — 

fcM-1— ^— tH 




COMSTOCK on the Azoic locks of Northwestern Wyoming, 515. 
than litholo^dcal for calling these rocks Laurcutiau, 515, 516, 

No reasons other 


Report hy Newton and Jenney on the Black Hills, 516 ; the Azoic rocks divided 
into Laurentian and Huronian, hnt on very slight evidence, 516. 


Results of the California Survey, 516, 517. Hunt's views in 1866, and in 1868, 
before visiting the region, 517. He spends several days there, ami discovers 
that ro.^vs of the Sierra Nevada whicai contain Jurassic fossils are of Huronian 
,<^e, 517, 518. Hunt's views of Califoniian geology shown to be iundamentally 


wrong, 518. 


Ei^suirf;, AND General Discussion. 

Introductory remarks, 519. The geology of CaimJa aud Ne^y England in an almost 
Ipelc.^ state of confusion, 619, 520. How this condition of t ungs has been 
hvoucdit about 520. The establishment of the Silurian System by MURCIIISON, 
in ] sV. or.cns the way to the discussion of the .luestion whetlun- the lowest lumt 
of life'lKul been reached, 520. First use of the term Azoic by. Mmuu.LSON, m, 
521- his dehnition of thn,t term, 621; his hesitating and contradictory statements 
in regard to it, 521 ; his gradual withdrawal of it in the successrve ediUous of 
SiluHa, 521, 622. BA.a.ANDE's grouiung, iu 184G, oi the Protozo.c and Azo.c 
rocks 522 ; confusion caused by the use of the term Cauibnan already begun .,22. 
FosTia-. and Whitney, in 1851, describe certain rocks on the south shore o Lake 
Superior, under the designation of the Azoic System, 622. Srnular roeks,^ ,n 
Canada, called by LooAN the Metanmrphic Series, but without lully aseer tarning 
their geological position, 523. LooAM, in 1864, applies the name LaurenUan to 
these rock:, 523 ; confusion introduced by his inabihty to d.stmgmsh between 
the Azoie and the Pakeozoic, 523. The term Azoic for some tm,e i" «"-;"* "- 
in this country, 523, 524; Dana's use and defnrition of it in 18«2 and 18.1, 624; 
his views in regard to tlu. <.xisleuce of life during an " azoic period, 524 ; the 
position assumed by bin, in 1874, and the introduction of tlu, term An a^ij, 
lith a delinition of it, 524. Confusion of views m regard to the older ciys 1- 
lin<. rocks, 525. Some general remarks introductory to the consideration of the 
II 5 5 ; great interest attaching to the question whether life exists m other 
worlds tlian our own, 625 ; importance of fixing the epoch when life began here, 



525. "WliJit is meant by the terra Azoic, and what rocks may be included under 
that desin;uation, 526, 527. How Fowtkr and Whitnky used the term Azoic, 
527. The condition of things in regard to the propriety of the use of that term, 
527. Injustice done by LouAN in liis introduction of the name Laurentian, 
527, 528. Discussion of the question wliethcr tlie term Arehiean ought to rcphico 
that of Azoic, 52S. Examination of the question, 528-538; lirst announce- 
ment of its existence by Lu{jan, in 1858, 528 ; Daavson, in 18()4, announces 
that it belongs to the Uluzopods, and tliat its discovery will be " one of the bright- 
est gems in the scieutiQc crown of the Geological Survey of Canada.," 529; furtlicr 
investigation of thu EozoiJn by Caupknteu, and its recognition by him as a 
Foranimifer, 529; his authority insures its gen(!ral recognition as the earliest 
known representative of life, 529; opposition, however, begins to manifest itself, 
529; gradual accumulation of an eozoonal literature, but general acceptance of 
the Eozoon Canadcnse, 530 ; dilhcrdty in tlio way of proving that it was not 
organic, 53,0 ; Iiow Jldiiius overcame this difllculty, 530, 531 ; his results, 
and tlie characterization of tlieni by Zittel and F. IvOEMKu, 631; Leidy'h views, 
531; our own investigations into the character of the " Eozoonal limestones " of 
Eastern Massachusetts, 532-534. Prevalent tendency among paheontoh^gists, at 
the present time, to lind traces of organic life in all kinds of rocks, such as 
granite, lava, and even in slag — tliis accounted for, 534. Some evidence in re- 
ard to the ability of Cahpenteu and Dawson to distinguisli minerals from 
fossils, 534-537. Extraordijuiry discoveries of Otto IIaiin, and their bearing 
on the Kozoon (piestion, 537, 538. Question discussed whether the existence of 
limestone and graphite is a proof of the presence of life at the time of their forma- 
tion, 538-544. Biscuof's views in regard to the existence of carbon during the 
primeval epoch, 538 ; his evidence controverted, 538-543; gniphite in cast-iron, 
538; in the crystalline rocks, 539; not formed as coal luis lieen, 540; phnuliago 
not always gra[)hite, 540; the artiiieial production of graphite, and of tluMlia- 
mond, 540 ; graphite formed in tlic he lilanc process, 541; JiistnioF's ideas in 
regard to the nmde of occurrence of tlie diamond ^siiown to be incorrect, 541, 
542; how it does oeeui-, in connection witli gohl, 512; in South Africa, in vob 
canic roidvs, 542, 543; some facts in rcganl to the peculiar circumstances uiuler 
which the dvanmnd umst have bctai formed, 543. Examination of the (airrcnt 
idea that the presenic of carbonate of lime is proof of tlie existence of life at the 
time tins was fornuHl, 543, 544. Shnilar imputy in jvgard to iron, 544 ; in 
regard to sulphur, 544, 545; phosphoric acid, 545. No encouragement given, 
by the investigations of the past half-ccntuiy, to the idea that below the 
Primordial or Potsdam zone there is another scries of fossilifcrous rocks, 545. 
The wisli father to the thought, 545, 540; Lyell "revels wltli delight" 
{JJde J\lurchison) at the discovery of the Kozoiin, 545. DilUeulty in which evo- 
lutionists are iilaceii by its adoption, 540 ; E. JioiGMKu's statement of the ease 
recommended for considcratimi, 54G. llemarkable result of pahcontological 
investigations— one and ihc ,sauu^ fauna over the whole globi; (Uning the Pri- 
nmrdial epoch, 546. lid'creiices with regard to the iizoic character of tlie Azoic 
series, 546. Tmpury into Dana's use of his term Archiiian, 547-550; he includes 
under that dcsignjition rocks of diQ'crent ages, both fossiliierous and non- 
fossiUf(U'ous, 547 ; the importance of recognizing in our nomenclature the epoch 
of the first iutroducniou of life upon the globe, 547. DaN/V believes that a part 



of the Archosan rocks arc fossiliferous, and states what tlic life of that epoch 
must have probably bo(!n, 548 ; his "abundance of life," however, only a theo- 
retical abundance, 548. All eruptive and cryytalline rockw, excejjt the meta- 
morphic Palaiozoic and post-PahtiOi^oic, aeoordiug to Dana, "Arehaian " 648 
649 ; nnphiloso^ihical chai'aetcr of this idea, 549, 550. 

Inquiiy into the propriety of the division of the Azoic (Archaean) into two or more 
groups, 550-560 ; according to Dana's views, this absolutely necessary, 550. 
Tiie atterapts.of the Canada Survey to do this on the evidence of fossils, 551 552- 
the AspiUclla and ArcnicoliicSj 551, 552. Geologi(;al time kept by the order of 
succession of life, and not by means of minerals, 652 ; the Canada Survey, and 
the results of its attempts to follow the hitter method, 552. 

How such metliods came to be in vogue, 552. By what principles the Canadian 
Surv('y was governed, 553, Louan the author of them, 553 ; with what train- 
ing he began it, 553, 554 ; his age at the time he published his first scientific 
jjaper, 554 ; the iulluenccs under which he worked, 554 ; he fulluws Lyell 
implicitly, 555 ; he b(;gins the work with certaiu theoretical assum[)tions, the 
truth of which he never investigates, 555 ; how his erroneous int(;r[)rotation of 
the geology of Lake Huron and Lake Superior led him to false conclusions, 556. 
The Keport of 1863 assumed certain things as having been proved which had 
not been, 556. Hunt's statements about his own or other jjenple's work not to 
be acci^pted as authority until his (piotations have been compai-ed with the 
oiigin.,''. authurities, 550. The (piestion of the noiK;()nfornjity of the Laurontian 
and Iluroniau looked into, 556 ; what omjiU to hi; seen if tlie two fi,ro uncon- 
formable, and what is seen, 556, 557 ; Skiavyn'h statements on this point, 557. 
"What takes [tlacc when eruptive rocks begin to be acted on Ijy erosive agencies, 
557. What basis of fact underlies the division of the Azoic rocks into two 
series, 558, 559. takes the ground that lithologiiiid characters are suEIi- 
ci(ait for the arraiig(^ment of J'ocks in chronological order, 559 ; iu accordance 
with this view, the rocks jireviously called Iluronian still farther dilferentiated, 
560; the gabbros thus separated, 560; the Hastings scries, demonstrated by 
Ykxnou to be cojitinuous with the Laui'cntian, made into the ]\lontalban and 
Taconian, 560 ; the Aivonian, 560. Tabular arrangement of the rocks as at 
present adopted by the Canada Survey, 561; some im]m>vcraents, and a carrying 
fai'ther forward of the same idea, suggested in another table, 562 ; eonnnents 
on this mode of work, 562. Importance to American geologists of having the 
work of the Canada Survey done according to better methods, 562. 

ArrKNDTX : Exa,mination of some of luvixo's statements, made in the Third Annual 
Ileport of the United States Geological Survey, 563-565. 

-nr -_ rr?^ r*- 

—r- ■* " Kv^ - 

~-^^rjTri Lfi- ■F.^v-M~iT-' ! '''j^[TJ~^|^'Il|7|^" 




Syno2')sis of the Evidence on which the Racks of the Azoic System 
have hecn variously grouped into Distinct Divisions hj American 

In" tlio following discussion the various regions where rocks of the 
Azoic System occur will be taken up and examined in a geographical 
order, beginning with that part of the North American coutinent where 
these rocks have their greatest development, and where, in course of 
a geological survey carried on continuously for more than forty years, a 
large portion of the material has been published which will here come 
under review. In order to prevent misunderstandings, and as an im- 
portant assistance to those who may hereafter wish to make an inde- 
pendent examination of the questions here discussed, the exact language 
of the author quoted will be given in as much fulness as seems desirable, 
although this course must necessarily considerably increase the length 
of this paper. 


Sir Wm. Logan, in the Report of Progress of the Canada Geological 
Survey for 1845-46 (pp. 40-51), described a series of rocks which he, 
following Lyell, called the *' Mctamorphio Series." This ho divides into 
two divisions, one composed in general of "sycnitic gneiss," the other of 
the same rock with intercalated bands of crystalline limestone. The 
relations of these to each other can be best expressed In Logan's own 
words : — 

" To the south of the Mattawa and of the Ottawa in \U continuation after 
the junction of tlie two streams, important beds of crystalline limestone become 
interstratificd with the syenitic gneiss, and their presence constitutes so marked 
a chasacter tliat it appears to me expedient to consider the mass to which they 
belong as a separate group of metamorphic strata, supposed from their geo- 
graphical position and general attitude to overlie the previous rocks conform- 
ably. The limestone beds appear to be fewer at the bottom than at the top 

BULL. MUS. COMP. Z0(3l. VOL. VII. — NO. 11. 







of the group, but whether few or many, they are always separated by beda 
of gneiss which in no way differs either in constituent quality or diversity of 
arrangement from the gneiss lower down, excej)t in regard to the presence of 
accidental minerals, the most common of which arc garnets." (/. c, pp. 41^ 42.) 

It is thus seen that his divisions arc arbitrary and theoretical, both 
being, according to his statement, conformable and intcrluminatcd with 
one another. As regards the origin of the " syenitic gneiss," or lower 
formations, he writes that they possess ''an aspect inducing a theoreti- 
cal belief that they may bo ancient sedimentary formations in an altered 
condition." (/. c, p. 40.) The lamination planes of the gneiss (?) ap- 
pear to be taken without hesitation as planes of sedimentation. As 
before, theoretic belief, and not evidence, was the basis on which all 
was decided, and Logan never went beyond this. 

Without adopting any theory of the origin of the rocks in question, 
it is sufficient simply to point out that, accepting Logan's own state- 
ments as true, the rocks might, so far as the jiublished evidence goes, 
have originated in any way not a priori impossible. Bis evidence is 
valueless excepting so far as credit may be given to the skill he may at 
that time have possessed in distinguishing metamorphic sedimentary 
from metamorphic eruptive rocks. 

Later he stated : — 

" The succession of rocks in ascending order, .... after crossing sixty-three 
miles, .... occupied by the unbroken uidformity of the lower metamorphic, 
or syenitic gneiss, formation, is as follows : — 

" 1. Chloritic slates and conglomerates. 

" 2. Greenish sandstones. 

" 3. Fossiliferous limestones." (/. c, p. 67.) 

The chloritic slates and conglomerates were said to nold pebbles and 
boulders of the subjacent gneiss. The limestones were regarded from 
their fossils as being of the age of the Niagara. Mr. Logan says ; 

" The facts that have aa yet come within my observation in res])ect to these 
formations have not been sufficient to enable me to determine to my own satis- 
faction what their relations are in respect to conformability. That the lime- 
stones are unconformable with the slates appears almost certain, but it is not 
in my power to state with which the intermediate sandstones are conformable, 
if they are so with either, or whether tliey are unconformable with both ; nor 
can I assert whether the slates are conformable with the gneiss." (/. c, p. 69.) 


Wo thus see that the chloritic slates and conglomerates, which later 
on lithological evidence were referred to the TTuronian, were only shown 
to be older than the Niagara, their true age being unknown. 

i 1 



Logan in the Eoport of Progress for 184G-47 described the series on 
the north shore of Lake Superior in ascending order, as follows {l. c, 

pp. 8-17) : 

" 1. Granite and syenite. 

*'2. Gneiss. 

" 3. Chloritic and partially talcose and conglomerate slates. 

"4. BluiHb slates or shales, interstiatified with trap. 

*' 5. Sandstones, limestones, indurated marls, and conglomerates, interstrati- 

fied with trap. 

" The rock at tlie base of the series is a granite, frequently passing into a 
syenite by the addition of horublenih', but the hornblende does not appear to 

be often present wholly without the mica The granite appears to pass 

gradually into a gneiss, which seems to participate as often of a syenitic as a 

granitic quality The gneiss is succeeded by slates of a general exteiior 

dark green colour, often dark-gray in fresh fractures, which at the base apj)ear 
occasionally to be intcrstratified with beds of a feldspathic quality, of the red- 
dish color belonging to the subjacent granite and gneiss Some of the 

beds have the quality of a greenstone, others that of a mica slate, and a few 
present the character of quartz rock. Rising in the series, these become inter- 
stratified with beds of a slaty character, holding a sulFicient number of pebbles 
of various kinds to constitute conglomerates. The pebbles seem to be of 

various qualities, but apparently all derived from hypogene rocks The 

formations which succeed, rest unconformably upon those already mentioned. 
The base of the lower one [No. 4], wdiere seen in Thunder Bay in contact with 
the subjacent green slates, presents conglomerate beds probably of no great 
thickness, composed of quartz pebldes chieHy, with a few of red jas})er, and 
some of slate in a green arenaceous matrix, consisting of the same materials in 
a finer condition." 


Eoposing on the bluish slates (No. 4) are "sandstones, limestones, 
indurated marls and conglomerates intcrstratified with trap," and 
crowned by an enormous amount of volcanic overflow. No evidence 
ia adduced to show that these two '* volcanic formations " are uncon- 
formable with each other, but sufhciont proof is cited to show that they 
are nnconformable with the granite, gneiss, and chlorite slate. The 
volcanic formations are, however, regarded as being older than the 
Potsdam sandstone. (Z. c, p. 34.) 

Logan further remarks : 

i;^ ;h 



. ■ 

" The chloritic shites at the summit of the older rocks on which the volcanic 
formations rest unconformably, bear a strong resemblance to those met with in 
the upper part of Lake Temiscamang on the Ottawa, and it appears probable 
they will be found identicah" (I. c, p. 34.) 




Logan evidently hold that the greenish slates (No. 3) were conform- 
able to and continuous with the underlying gneiss, one rock passing 
into the other ; while the conglomerates observed were not at the base 
of the slatcSj but quite high in the scries. (Geol. of Canada, 1863, 
pp. 52-55, G4.) Dr. Hunt's language in his ^' Azoic Rocks" (p. 68) 
implies that Logan found a different relation between the gueiss and 
slate, — namely, unconformability with the conglomerate at the base. 

Mr. Alexander Murray in the same report (184G-47) states that the 
rocks in the basin of the Kamanistiquia River are granite, syenite, 
gneiss, micaceous and chloritic schist, overlain by blackish argillaceous 
slates with associated trap. 

Of the first series he says : 

" AVhero they make their appearance at the lower end of the portage, the 
character of the rock is a red or in some iiiBtances a whitish massive syenite, 
which passes gradually into a gray gneissoid syenite, dipping at a high angle 
N. N. W. ■ Resting conformably on the gneiss, there occurs a series of dark 
greenish blue or greenish black altered slates, the one rock passing almost im- 
perceptibly into the oilier Towards the bottom near the junction with 

the syenitic portion, the slates are of a dark bluish and occasionally of a brown- 
ish color. They appear to be highly altered." 

Of the black argillaceous slates Mr. Murray says : 

^' The base of this formation .... was observed on the Kamanitiqnia near 
the Grand Falls. Its immediate junction with the rock on which it reposes 
was concealed from view, but appears to be indicated by the position of a small 
lake or pond, occurring just below the second portage, and the niai'shy ravines 
which run from it in the direction of the strike on each side. The slates vis- 
ibly reach to within a short distance of the pond, i)robably brought into place 
against the syenite by a dislocation." {l. c, pp. 51-53.) 

The syenite and gneiss afterwards were assigned to the Laurentian, 
and the greenish blue or greenish black slates to the Huronian. Hence 
wo see that at the only contact known for many years of the Laurentian 
and Huronian both series were conformable, passing almost wipcrceptihhj 
into one another. Also, that near the junction the slates were highly 
altered. (Geol. of Canada, 1863, p. 64.) These facts are not men- 
tioned by Dr. Hunt in his account of this report. (Azoic Rocks, pp. 
68, 69.) It is, however, to be kept in mind, that at this time, as also 
when the Huronian was named and for some years later, Nos. 4 and 5, 
or the black slates, sandstones, traps, conglomerates, etc., constituting 
the copper-bearing scries (Kewcenawan, but really Potsdam) were held 
to be the exact equivalents of the schists and slates (Huronian) north of 

^rr. ^ ^"^^~J" 

•j^- _ 




I ,1 

Lake Superior, while the above greenish slates (No. 3) were not sepa- 
rated from the preceding rocks (Nos. 1 and 2) until many years later. 
(See Am. Jour. ScL, 1852, (2 ) XIY. 224-229 ; 1857, XXIIL 305-314; 
Azoic Rocks, pp. 71, 72, SO.) 

In the Keport of Progress for 1847-48, Mr. Murray gives some ac- 
count of the sequence of the rocks on the islands and northern shore of 
Lalvo Huron. 

*' Tlio older groups observed consist, firstly, of a metarnorpliic scrioR, com- 
posed of granitic and syenitic rocks, iu the forms of gneiss, mica slate, and 
horublendo slate ; and, secomlly, of a straiiried series composed of (]_uartz rock 
or sandstones, conglomerates, shales and limestones, with hiterposed beds of 
greenstone ; " 

succeeded by fossilifcrous formations, i. c. Potsdam sandstone, etc. 
Certain of the conglomerates of the second series arc said to contain 
pebbles and boidders of syenite, but beyond this nothing is advanced to 
show the relations of this to the granitic and syenitic rocks, the two 
scries not being seen in contact. The relation of ihc fossilifcrous forma- 
tions to the preceding series was shown clearly enough, the separation 
being a marked one. (/. c, pp. 107—113.) 

Mr. Murray further says : 

*'0n a cluster of small islands .... Granite, [lithologically like the 

Laurcntian,] was found breaking through the (p.iart/-rock The colour 

of ilie rock was red. On one of the islands, qnartz-rock beds on opposite 
sides of the granite were observed Lo dip in opposite directions, north on the 
north side and south on the south side, at an angle of 70° or 80° ; and in an- 
other of the islands the cpiartz-rock and gi'anile were seen in juxtaposition, the 
former reclining on the latter. In liiis case the (ptartz rock was traversed by 
several trap dykes running sli-iilly obhcpie to the strike, while granitic veins 
ran transversely tlirough the wlii*le, and were continued throu^-h a main bmly 
or unclcus (if granite, the one gvaiute being distinguishable from the other, 
notwithstanding the red color of both, by the fmer texture of the veins." {I. c, 
pp. 112, 113.) 

In a "Report on the North Shore of Lake Huron," under date of 
December 20, 1848, Mr. Logan gives some account of the second series 
described by Mr. Murray, and states : 

"Tlie series of rocks occupying this country from the connecting link be- 
tween Lakes Huron and Superior to the vicinity of Bhebawenahning, a distance 
of ]20 miles, with a breadth in some places of ten, and in others exct-ediug 
twenty milesj it appears to me, must be taken as belonging to one forma- 

' ■! 

D. r 


z£ u ' '-^ 

^^^—jbb^ ^ ^ ■■■ ij ^r-rr.r-^ 

J ^_x ^-n^^_L^i^^n ^ — 



tion ; on tlie west it seems to repose on the granite, whicli was represented in 
my report on Lake Superior as running to the east of Gros Cap, north of Sault 
Stc. Marie ; on the east the same supporting granite was obst^rved by Mr. 
Murray north of La Cloche, between three and four miles in a straight line up 
the Eivicre an Sable, .... and again, about an equal distance up another 
and parallel tributary, .... in both cases about ten miles from tlie coast. 
. . . . In respect to the geological age of the formation, tlie evidence alforded 
by the facts collected last year by Mr. Murray .... is clear, satisfactory, 
and indisi)utably conclusive, .... successive formations of the lowest foRSil- 
iferous group of North America, were each in one place or the other found, m 
exposures divested of all vegetation, resting in unconformable repose, in a 
nearly horizontal position, upon the tilted beds, and undulating surface of the 
(luart/ rock, and its accompanying sti'ata, filling up valleys, overtopping momi- 

tains, and concealing every vestige of dykes and copper veins The 

chief diilerence in the copper-bearing rocks of Lakes Huron and Superior, 
seem to lie in the great amount of aniygdaloidal trap present among the lat- 
ter, and of white (luartz rock or sandstone among the former. But on the 
Canadian side of Lake Superior there are some considerable areas, in which 
important masses of interstratilied greenstone exist without amygdaloid, while 
white sandstones are present in otliers, as on the south side of Thunder 15ay, 
thou<di not in the same state of vitrification as those of Huron. But notwith- 
standing these ditferences, there are such strong points of resemblance m the 
interstrraihcation of igneous rocks, and the general minerahzed c<,iKhtiou of 
the whole, as to render their positive or proximate e(iuivalence highly probable, 
if not almost certain ; and the conclusive evidence given of the age oi the 
Huron wouKl thus appear to settle that of the Lake Superior rocks, m the 
position given to them l)y Dr. Houghton, the late State Geologist oi Michigan, 
as beneath the lowest known fossilifer.Ris deposits, a position wliich, as will be 
seen by a reference to the Keport of Progress I had the honor to submit to 
your Excellency in 184G, appeared tome to derive some support from evideuces 
on the Canadian side of Lake Superior itself." (l. c, pp. 8, 9, 10, 20.) 

In this is to be seen one of the attempts to decide geological ago by 
lithological evidence, applied to rocks at great distances from one un^ 
other, — a failure, in this case at least, as will bo seen farther on. One of 
the writers has pointed out olscwberc that the statements in this report 
and in that for 184G-47 (p. 34) regarding Dr. Houghton's views are 
erroneous. (Ihill Mus. Gomp. Zool. 1880, VIL ((Jeol. Series L) 83.) 
The views which Logan held regarding the age of the copper-bearing 
rocks of Lake Superior at Hie time of the publication of the report from 
which quotations have just been made, were published later in several 
papers. (Bull Soc. Geol. France, 1849-50, (2 ) VIL 207-209. Report 
Brit. Assoc. Adv. Soi., 1851, Trans. Sec., pp. 59-G2. Am. Jour. 8c.., 
1852, (2 ) XLV. 224-220.) Li these publications the copper-bcanng 

jt \n^ _ _\ 

1^'^ ^' I- I- 




rocks of Lake Huron, and therefore those of Lake Snperior, were re- 
garded as being of Cambrian age. 

In the lleport of Progress for 184:8-4:9, Mr. Murray again reported 
on the region north of Lake Huron. He arranges the rocks along the 
Spani^li Itiver into two series : the granitic or metamorpliic group, and 
the quartz roch group. The first group "appeared to rise from beneath 
the rocks of the second group in two different locahties," but no evidence 
seems to have been found to show the relations of the two supposed 
formations except the finding of pebbles of granite or sj^enite in some of 
the conglomerates of the second group. The rocks of the first group 
were said to be granite or syenite, except the following : — ■ 

" A gneisaoitl structure was observed on one or two occasions, but it was for 
the most part obscure and ill-defined, being perceptible rather in a longitudinal 
arrangerneut of the constituent minerals, than in conspicuous beds of different 
r[uulity." (/. c, pp. 3C-42.) 

In the Report of Progress for 1849-50, a ti'act of country on the St. 
Lawrence lUver, between Bay St. Paul and Murray Bay, was described. 
Hero the metaraorphic group, consisting of gneiss, was overlain by 
white quartz rock (Potsdam sandstone). {I. c, pp. 8-10.) In the Re- 
port for 1851-52, the inetamorjMc or gneissoid group is likewise said 
to be overlain by Potsdam sandstone in the country between Bcauhar- 
nois and the Riviere du Nord. {L c, p. (J.) 

In tlie Quarterly Journal of the Geological Society (Vol. VIIL, 1852, 
p. 210), Mr. Logan states regarding the rocks north of Lake Huron : 

" Ou Lake IJuron the Lower Silurian group rests unconTormably upon a 
siliceous series with only one known band of limestone, of about 150 feet 
thick, with leaves of chert hi abundance, but as yet without discovered 
fossils. This scri(!S is supposed to be of the Cambrian epoch. It compre- 
hends the copper-bearing rocks of that diytrict, and with its igneous inter- 
stratilied masses has a thickness of at least 10,000 feet. The gneissoid group, 
of wliich nientiou is made, is probably still older than this. Its conditions 
appear to me to mnko it reasonable to suppose that it consists of aqueous de- 
posits in an altered state." 

In the Report for 1852-53, but published in 1854, Mr. Logan 
writes : — 

" The name which has been given in previous Reports to the rocks underly- 
ing the fossiliterous formations in this part of Canada is the Metannn-phic 
Bcries, but inasnnicli as tliis is applicable to any series of rocks in an altered 
condilion, and miglit occasion confusion, it has been considered expedient to 
apply to them for the future, the more distinctive appelhition of the Lauren tian 

VOL. VII. — NO. 11. 22 











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=.-±\^, -■^'T ■ A n-" 



series, a name founded on that given by Mr. Garncan to the chain of hills 
which they compose. The geological formations which underlie the district in 
ascending order would thus be as follows : — 

"1. Lauren tian series. 

** 2. Potsdam sandstone/' etc. (/. c, p. 8.) 

It will thus be seen that when the name Laurcntian was thus pro- 
posed, it was the exact equivalent of the Azoic of Foster and Whitney 
proposed four years before. 

In *' A Sketch of the Geology of Canada," by Dr. Hunt, occurs the 
first mention of the Huronian system as such. 

"The shores of Lakes Huron and Superior offer a series of schists, sand- 
stones, limestones and conglomerates interstratificd with heavy l)edy of green- 
stone, and resting unconformably upon the Laurentian formation. As these 
rocks underlie those of the silurian system, and have not as yet alforded any 
fossils, they may i)robably be referred to the Cand)rian system (lower Cam- 
brian of Sedgwick.) This Huronian formation is known for a distance of 

about 150 leagues upon Lakes Huron and Superior, and everywhere offers 
metalliferous veins, which have as yet been very little explored." (Canada at 
the Universal Exhibition of 1855, pp. 427, 428.) 

In the same paper Dr. Hunt says of the Laurentian system : — 

" The rocks of this system are, almost without exception, ancient sedimentary 
strata, which have become highly crystalline." (p. 421.) 

So far as we are able to find in the Reports of the Canada Geological 
Survey no evidence was advanced to prove this position ; it was a purely 
theoretic assumption, as Logan states (ante, pp. 331, 332). Dr. Hunt 
also declares that the Huronian on tlie shores of Lakes Huron and Su- 
perior rests unconformably upon the Laurentian formation. This too 
was a theoretical belief instead of an observed fact, so far as the Reports 
bore evidence (p. 427), except in the case of the Lake Sui)erior copper- 
bearing rocks (Keweenawan, Potsdam), at that time regarded as being 
the equivalent of the schists (Huronian) north of Lake Huron. (See 
Azoic Rocks, pp. 71, 72 ; also ante, pp. 334, 335.) 

Of the chlorite schists in the valley of Lake Teraiscaming it is writ- 
ten : — 

*' The chloritic schists probal)ly correspond to the Huronian rocks, but it is 
difficult to fix the age of the sandstones which are destitute of ioasils." (/. c, 
p. 447.) 

The first mention of the Huronian formation by name, found in the 
Reports of Progress of the Canada Geological Survey, is in Mr. Murray's 
Report for 1854, under date of June 11, 1855, (p. 125,) as follows : 

■^'- '■ "^--' ^ ■' 



" Among tlie Louklcrs ou Lake Nipissing, many were o'bsGrvei.l to "be of a 
elate conglomerate, and they were fretj^uelitly of very great size ; in their as- 
pect and general character these have a very strong resemblance to the slate 
conglomerate of the ITuronian series, from which in all probability, they are 

The next mention is in tlio Ecport for 1855, dated March 1, 1856, 
p. 134 : 

" The pebbles and bonlders of metamorpliic rocks which abound in the 
gravel and clay deposits, and are numerously scattered over the surface, are 
clearly derived from the Laurehtian and Iluronian formations on the north 

shore of Lake Huron." 

In the Ileport for 1856 (March 1, 1857, pp. 1G8, 172) it is stated : 

" Tlie rocks of the region explored during the season, embrace two of the 
oldest recognized geological formatios, the Laurentian and Huronian. .... 
The difference in lithoh)gical character between the two formations was always 
SuITiciently apparent, but thougli both were frequently found at short distances 
apart, the immediate point of contact wasaWays obscure ; and a mass of green- 
stone of rather coarse grain was usually the fu-st intimation pf the proximity 
of the higher rocks Whether this greenstone is the result of an over- 
flow contemporaneous with the upper formation, or an eruptive mass intruded 
at a later period, has not yet been ascertained." 

Eegarding the hypersthene rock which lias since been set apart as the 
tipper Laurentian or Norian Series, Dr. Hunt in his Ileport for 1854 
(April 1, 1855, p. 374) states : 

*' The rocks about to be described belong to the crystalline strata of the 
Laurentide mountains, and occur, as far as yet observed, in close association 
■with the crystalline limestones, which alternate with the gncissoid and ouart- 
zosc rocks of the formation." 

In Dr. Hunt's Report for 1§56 (April 1, 1857, p. 451, see also Philo- 
Bophical Magazine, 1855, (4) IX. 354, 355), it is written concerning 
the same rocks ; — 

*' In the Report for 1854 I have described at some length a class of stratified 
felspatliic rocks, which form an important part of tlie Laurentian series, and 
are associated with the calcareous and magnesian deposits of that ancient 

The Reports here rcfciTcd to from 1853 to 1856 were not published 
until 1857. 

The division of the Azoic rocks into Laurentian and Iluronian, and 
Logan's view that the copper-bearing rocks of Lake Superior were of 



n ^11 

I'. y\ 

\i li ! 



HA X ^r 

■ ^^^ — n 1^— ^^ 



the same age as the Huronlan rocks of Lake Huron, were opposed the 
same year by one of the present writers in the May number of th( 
American Journal of Science (1857, (2) XXIIL 305-314). He als: 
pointed out Logan's violation of the law of prioiity in appropriating the 
term Laurontian from Desor.* It was there shown that the reason Logan 
had for separating the Huronian from the other Azoic rocks was his 
(Logan's) belief that the copper-bearing rocks (Potsdam) of Lake Supe- 
rior were the same as the Azoic schists north of Lake Huron : hencC; as 
the copper-bearing rocks of Lake Superior rested unconformably on 
Azoic granites, etc., therefore the Lake Huron rocks must. Later, Logan 
abandoned his premises, but did not, however, give up his conclusion. 

(See Hunt, Azoic Rocks, p. 80.) 

In the Proceedings of the American Association for the Advancement 
of Science (August, 1857, pp. 44-47), Mr. Logan made some statements 
regarding *' the division of the Azoic Rocks of Canada into Huroniau 
and Laurentian," the chief of which we reproduce here : 

'* The sub-Silurian Azt)ic rocks of Canada occupy an area of nearly a quarter 
01 a million of square miles. Independent of their stratification, the parallel- 
ism that caji be shown to exist, between their lithological character and that of 
nietamorphic rocks of a later age, leaves no doubt on my mind that they are a 

series of ancient sedimentary deposits, in an altered condition So. 

early as the year 1845, as will be found by reference to my report on the 
Ottawa district (presented to the Canadian government the subsequent year), 
a division was drawn between that portion which consists of gneiss and its 
subordinate masses, and that portion consisting of gneiss interstrutified wit,h 
important bands of crystalline limestone. I was then disposed to place the 
lime-bearing aeries above the uncalcarcous, and although no reason has since 
been found to contradict this arrangement, nothing has been discovered espe- 
cially to confirm it. ... . In the same report is mentioned, among the Azoic 
rocks, a formation occurring on Lake Temiscaming, and cpnsisthig of silicious 
slates and slate conglomerates, overlaid by pale sea-green or slightly greenish- 
white sandstone, with quartzose conglomerates. The slate conglomerates are 
described as holding pebbles and boulders (sometimes a foot in diameter) de- 
rived from the subjacent gneiss, the boulders displaying red feldspar, translu- 
cent quartz, green hornblende, and black mica, arranged in paralhd layers, 
which present directions according with the attitude in which the boulders 
were accidentally inclosed. From this it is evident that the elate conglomer- 
ate was not deposited until the subjacent formation had been converted into 

* Tliis paper of Prof. Whitney's, in common with some others, was accidentally 
omitted in Mr. WadswortVs "List of Papers " appended to the " Kotes on the 
Geology of the Iron and Copper Disfiicts of Lake Superior," although reference was 
made to it in the text. (See also Canadian Journal, 1857, (2 ) IL 302.) 



gneiss, and very probably greatly disturbed ; for while the dip of the gneiss, 
up to the immediate vicinity of the slate conglomerate, was usually at high 
angles, that of the latter did not exceed lunc degrees, and the sandstone above 
it was nearly horizontal. In the Keport transmitted to the Canadian govern- 
ment in 1848, on the north shore of Lake Huron, similar rocks are described as 
constituting the group which is rendered of such economic importance, from 
its association with copper lodes. This group consists of the same silicious 
slates and slate conglomerates, holding pebbles of syenite instead of gneiss, 
similar sandstones, sometimes showing ripple marks, some of the sandstones 
pale-red green, and similar quartzose conglomerates, in which blood-red jasper 
pebbles become largely mingled with those of white quartz, and in great moun- 
tain masses predominate over them. But the series is here much intersected 
and interstratified with greenstone trap, which was not observed on Lake 

Temiscaming The group on Lake Huron we have computed to be 

about 10,000 feet thick, and from its volume, its distinct lithological charac- 
ter, its clearly marked date posterior to the gneiss, and its economic impor- 
tance as a copper-bearing formation, it appeal's to me to require a distinct 
appellation, and a separate color on the map. Indeed, the investigation of 
Canadian geology could not be conveniently carried on withi)ut it. We have, 
in consequence, given to the series the title of linronian. A distinctive name 
being given to this portion of the Azoic rock, renders it necessary to apply one 
to the remaining portion. The only local one that would be appropriate in 
Canada is that derived from the Laurentide rancjo of mountains, which are 
composed of it from Lake Huron to Labrador. We have, the- ^fora, designated 
it as the Lanrentian series." (See also Canadian Journal, 1657, (2 ) II. 43Q- 
442 J Canadian Nat. and GeoL, 1857, IL 255-258.) 

Tho logic of the last few seiitcnccs will appear to be of a somewhat 
peculiar character, when it is remembered that the name "Lanrentian" 
had been adopted some two years before the name *' Huroniau " was 
used and some four years before Mr. Logan's papci: was read. 

As we have pointed out before, tho age of the Lake Temiscaming 
slates was unknown. 

In the same Proceedings Mr. Logan published a paper " On the Trob- 
able Subdivision of the Lanrentian Series of Kocks of Canada." Some 
limestone and associated labradorite rocks he would set apart, but does 
not propose any name for them. This division seems to be a local one 
based on lithological characters, as no evidence' was advanced to show 
tliat this formation was not conformable with the remainder of the 
Lanrentian, as it had been stated to be before. (Proc. Am. Assoc. Adv. 
Sci., 1857, XL 47-51 ; Canadian^JournaJ, 1858, (2) IIL 1-5 ■ Cana- 
dian Nat., 1857, IL 270-274.) 

Dr. J, J. Bigsby, in 18G2, regarded the Iluroniau as distinct from the 

^ I .1 




. .1 


^ ^ 

J \. 





Cambrian, and intimately related to the Laurentian, giving among liia 
reasons its marked similarity, lithologically, to the Laurentian, and the 
conformity of the Laurentian and Ilurouian ; and stating that in the 
only place north of Lake Superior where the two systems have been 
seen in contact, they were found r^nformable. (Quart. Jour. (jJeol. Soc, 
18G3, XIX.3G-52,) 

Two other localities spoken of by Dr. Bigsby were hypothetical, not 
actual observed contacts, as he supposed. (See Report on the North 
Shore of Lake Huron, 1849, pp. 8, 9; Report of Progress, 1848-49, 

p. 36.) 

In the Report on the Geology of Canada, 18G3, the so-called gneisses 
of the Laurentian series are assumed to be stratified, and although the 
acknowledgment is made that the supposed beds " when thick, which 
they usually are, might on first inspection be mistaken for intrusive 
igneous instead of altered sedimentary masses." That they are really 
sedimentary is supposed to be shown by the minerals being obscurely 
arranged in parallel lines " confornuible with the more distinctly banded 
portion of the strata." {I. c, p. 23, See also p. 587.) 

In fact Mr. Logan states . *' The rocks which compose the Laurentian 
mountains were shown by the Geological Survey, in 184G, to consist of 


a series of metamorphic sedimentary strata, underlying the fossilifcrous 
rocks of the Province." We have pointed out that nothing of the kind 
was shown by the Survey ; but that there was only an announcement 
of "a theoretic belief that they may be ancient sedimentary formations 
in an altered condition." (Gedl. Survey of Canada, 1845-4G, p. 40, 
18G3, p. 22 ; Azoic Rocks, p. G6 ; ante, p. 332.) 

Mr. Logan further states, that it is difficult north of Lake Huron to 
distinguish the Laurentian gneiss from an intrusive granite. (GeoL of 

Canada, 1863, p. 6L) 

Regarding the relation of the Iluronian to the Laurentian nothing 
that can be called evidence is advanced, except in one place ; but, as 
usual, some general assertions are made. The following extract will 
give an idea of what was actually known of the relations of the two 
formations, with the exception to be mentioned later. 

" In that part of the country on the north shore of Lake Huron which lies 
between Misyissagui and St. Mary Rivera, where the Huronian series has Ijeen 
more completely examined than elsewhere, the immediate contact of the gneiss 
with the overlying rocks has not been observed. On the coast line between 
the Mississagni and Thessalon Rivers, a distance of about twenty-five miles, 
the gneiss extends from within about four miles of the former to within about 



the same distance from the latter ; but it is very much disturbed by intrusive 
granite and greenstone, and, although there are great exposures of rock, it is 
very difficult to make out hcnv the stratified portions are related to one an- 
other. The gneiss extends to the vicinity of a small stream about a mile and 
a half above Les Grandes Sables, and what is supposed to be the lowest IIu- 
ronian mass of that part occurs about half a mile above the stream. It consists 
of a grey quartzite which abuts against one mass of gneiss and runs under an- 
other, and appears to be nmch broken by and entangled among the intrusive 
rock ; but judging from a transverse measure in one part, its thickness would 
not be far from 500 feet." (I. c, p. 55.) 

It would seem that licro the Huronian was found abuttiu'^ airainst 
and underlying the Laurentian gneiss (granite). In none of the sec- 
tious given do the conglomerates in the Iluronian appear to lie at the 
base of t\w formation, but at varying heights in the scries. 

The exception referred to above is this : under the head of " Contact 
of Laurentian and Huronian Rocks/' it is stated that in the upward 
navigation of the Kaministiquia Eiver 

*' the first development of the Laurentian series occurs at the second port- 
age, about half a mile above the Grand Falls. At the lower end of the port- 
age, where tlie series makes its appearance, the rock resembles a massive 
syenite, in some ]);i.rts red and in others whitish, but is probably a hornblcudic 
gneiss in wliioh the lamellar arrangement of the constituent minerals is ob- 
scure, as the rock graibuLlly passes into such a gneiss. Resting on it conform- 
ably there occurs a series of dark greenisli-bhie or greeuish4)lack slates, the 
one rock passing almost imi)erccptibly into the other. The section occupies 
upwards of a (quarter of a mile on the river bank, and at the upper end of it, 

as well as at the head of the portage, the dip is N. 54^ E At each 

rapid part of the river above the Grand Falls there is a greater or less develop- 
ment of those rocks, nu^st frequeully presenting the more distinctly stratified 
part of the gneiss. The best exposure of the slates is at the Three Discharges, 
about four miles above the Grand Falls, where the rocks are observed to pass 

from the gneiss to tlie slate Towards the bottom, near the junction 

with gneiss, the slates are of a bluish and occasionally of a brownish color." 
(I. c, pp. 64, 05.) 

It Avould then appear that Huronian in the only localities, except one 
problematical one (/. c, pp. 52-54, 703), in which it had been seen in 
contact with the Laurentian, was conformable with and passed almost 
imperceptibly into, or else underlaid, the Laurentian. 

An intrusive granite is said to occupy 

" a considerable area on the coast of Lake Huron, south of Lake ?akowa<?aminct. 
It there breaks through and disturlja the gneias of the Laurentian series, and 

ir ir. ^x-rr. 



forms a niicleus from which emanates a complexity of dykes, proceeding to 
considerable d